CN220656164U

CN220656164U - Dialysis tube fixing device

Info

Publication number: CN220656164U
Application number: CN202321725243.2U
Authority: CN
Inventors: 刘丹; 张静; 王龙真
Original assignee: First Affiliated Hospital Of Baotou Medical College Inner Mongolia University Of Science And Technology
Current assignee: First Affiliated Hospital Of Baotou Medical College Inner Mongolia University Of Science And Technology
Priority date: 2023-07-03
Filing date: 2023-07-03
Publication date: 2024-03-26
Anticipated expiration: 2033-07-03

Abstract

The utility model discloses a dialysis tube fixing device, which comprises a limiting mechanism capable of being worn on an arm and a positioning mechanism for fixing a dialysis tube, wherein the positioning mechanism is arranged on the limiting mechanism; before dialysis, the patient can be crooked to a comfortable angle with the arm, and the adjustable chuck on the stop gear can be fixed to this angle with thereby prevent that patient's arm from moving in disorder and arousing the aversion of dialysis pipe, and further, positioning mechanism accessible vacuum adsorption is in order to fix the dialysis pipe, is different from the fixed dialysis pipe of mode through the centre gripping in the prior art, can avoid reducing its internal diameter when fixing a position the dialysis pipe, can maintain great blood flow in the assurance dialysis pipe, guarantees that the blood flow is smooth and easy.

Description

Dialysis tube fixing device

Technical Field

The utility model relates to the technical field of medical instruments for nephrology department, in particular to a dialysis tube fixing device.

Background

Kidneys are one of important organs of human body and are responsible for removing wastes and metabolites in the body and maintaining physiological functions such as water balance, electrolyte balance and the like. When renal function is severely impaired or disabled, wastes and toxins in the patient's body cannot be normally discharged, and various serious diseases are caused, even life-threatening. Hemodialysis is a common kidney replacement therapy, which is mainly used for treating patients with renal failure.

Hemodialysis is performed by a special machine (called a hemodialysis machine) that draws the patient's blood from the body, passes it through special filters, removes waste and toxins from the body, and returns the cleaned blood to the patient. This process typically takes several hours, two to four times per week, with the specific frequency and time being dependent on the patient's condition.

Hemodialysis generally has two modes: venous (AV) dialysis and peritoneal dialysis. AV dialysis uses an arteriovenous bridge as the input and output of the dialysis machine, while peritoneal dialysis infuses dialysate into the abdominal cavity by leaving tubes in the abdominal wall, adsorbing and draining waste from the peritoneal cavity.

When carrying out the hemodialysis on vein way, medical personnel often need use medical sticky tape or dressing to fix the dialysis tube in the arm outside, and fixed effect is poor, causes the dialysis tube to shift easily when patient's arm activity, and then causes the original puncture position of needle insertion department skew for the patient appears discomfort or pain, needs adjustment position appearance or dialysis tube's position from time to time, has influenced the efficiency of dialysis.

Based on the above-mentioned shortcomings, how to effectively fix the dialysis tube becomes a technical problem to be solved.

Disclosure of Invention

The utility model discloses a dialysis tube fixing device which is used for solving the problem of poor fixation of a dialysis tube outside a body when dialysis is carried out through a venous line in the prior art.

In order to solve the problems, the utility model adopts the following technical scheme:

providing a dialysis tube fixing device, which comprises a limiting mechanism and a positioning mechanism;

the limiting mechanism comprises a first arm fixing plate, a second arm fixing plate and an adjustable chuck which are arranged in pairs, the adjustable chuck comprises a first support arm and a second support arm which can rotate relatively, the first support arm and the second support arm are respectively and fixedly connected with the first arm fixing plate and the second arm fixing plate, the adjacent first arm fixing plates and the adjacent second arm fixing plates are connected through elastic belts, the oppositely arranged first arm fixing plates are used for circumferentially clamping the large arm, and the oppositely arranged second arm fixing plates are used for circumferentially clamping the small arm;

the positioning mechanism is fixedly connected to the outer side face of the first arm fixing plate and/or the second arm fixing plate, the positioning mechanism is tubular, the length direction of the positioning mechanism is parallel to the length direction of the first arm fixing plate and/or the second arm fixing plate, the positioning mechanism comprises a rigid shell and a flexible positioning part, a vacuum exhaust valve is arranged on the rigid shell, a plurality of vacuum adsorption ports are arranged on the inner side wall of the flexible positioning part, and the vacuum adsorption ports are used for carrying out vacuum adsorption on the outer side wall of the dialysis tube.

As the preferable technical scheme, the first arm fixing plate and the second arm fixing plate are arc-shaped plates, and the arc length of the first arm fixing plate is larger than that of the second arm fixing plate.

As the preferable technical proposal, one side of the oppositely arranged first arm fixing plates is connected by an elastic belt, and the other side of the oppositely arranged first arm fixing plates is connected by a nylon flannelette bandage with a sticking buckle;

one side of the second arm fixing plate which is arranged oppositely is connected through an elastic belt, and the other side of the second arm fixing plate which is arranged oppositely is connected through a nylon flannelette bandage with a sticking buckle.

As the preferable technical scheme, adjust the chuck and include upper cover, the lower cover, first gear, the second gear, first pivot, the second pivot, first transmission shaft, the second transmission shaft, first support arm, the second support arm, wherein, first pivot sets up perpendicularly in the lower cover with the second pivot, first gear can rotate around first pivot, the second gear is connected with first gear meshing, the second gear can rotate around the second pivot, first transmission shaft one end rigid coupling is in first gear upper portion, the other end rigid coupling of second transmission shaft is in first support arm lower part, second transmission shaft one end rigid coupling is in second gear upper portion, the other end rigid coupling of second transmission shaft is in second support arm lower part, first support arm and second support arm set up in the outside of upper cover, the second gear can drive the second support arm rotation.

As the preferable technical scheme, the novel gear locking mechanism further comprises a spring and a spring shaft pin, wherein the spring is arranged in the upper cover, the upper end of the spring shaft pin penetrates through the upper cover, the middle part of the spring shaft pin is fixedly connected with the bottom of the spring, and the bottom of the spring shaft pin can penetrate through the first gear, so that the first gear is locked.

As the preferable technical scheme, the rigid shell is tubular, two ends of the rigid shell extend inwards in the circumferential direction, the flexible positioning part is provided with a cavity, and the outer side of the flexible positioning part is connected with the vacuum exhaust valve.

As the preferable technical proposal, the vacuum adsorption port is arranged in a strip shape along the axial direction of the flexible positioning part;

or the vacuum adsorption port is annular and arranged along the circumferential direction of the flexible positioning part.

As a preferred solution, the inner diameter of the flexible positioning part is adapted to the outer diameter of the dialysis tube.

As a preferred embodiment, the flexible positioning portion comprises a rubber material or a silicone material.

As a preferred technical scheme, at least two positioning mechanisms are arranged on the first arm fixing plate and/or the second arm fixing plate side by side.

The technical scheme adopted by the utility model can achieve the following beneficial effects:

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings required for the description of the embodiments are briefly described below to form a part of the present utility model, and the exemplary embodiments of the present utility model and the description thereof illustrate the present utility model and do not constitute undue limitations of the present utility model. In the drawings:

FIG. 1 is a schematic view showing the structure of a dialysis tubing fixture in a preferred embodiment of the present utility model;

FIG. 2 is a view showing a state of use of the dialysis tubing set according to a preferred embodiment of the present utility model;

FIG. 3 is a schematic view showing the internal structure of an adjustable chuck in a preferred implementation of the embodiment of the present utility model;

FIG. 4 is a cross-sectional view of an adjustable chuck in a preferred implementation of an embodiment of the utility model;

fig. 5 is a schematic structural view of a positioning mechanism in a preferred embodiment of the present utility model.

The method specifically comprises the following reference numerals:

the first arm fixing plate 10, the second arm fixing plate 20, the adjustable chuck 30, the first arm 31, the second arm 32, the first gear 33, the second gear 34, the first rotation shaft 35, the second rotation shaft 36, the first transmission shaft 37, the second transmission shaft 38, the spring shaft pin 40, the spring 50, the elastic band 60, the positioning mechanism 70, the rigid housing 71, the flexible positioning portion 72, the vacuum suction port 721, the vacuum exhaust valve 73.

Detailed Description

In order to make the objects, technical solutions and advantages of the present utility model more apparent, the technical solutions of the present utility model will be clearly and completely described below with reference to specific embodiments of the present utility model and corresponding drawings. In the description of the present utility model, it should be noted that the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

In the description of the present utility model, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present utility model will be understood in specific cases by those of ordinary skill in the art.

It will be apparent that the described embodiments are only some, but not all, embodiments of the utility model. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

At present, when hemodialysis of a venous line is carried out, a dialysis tube is left outside an arm, at present, when the dialysis tube is fixed, a dialysis tube clamp or a fixer can be used, and the dialysis tube clamp or the fixer can be used for fixing and supporting the dialysis tube, but the tube wall of the dialysis tube is extruded when the dialysis tube is clamped, so that the inner diameter of the dialysis tube is reduced, the blood flow is reduced, and the stability is poor; another means is to attach a transparent dressing tape to the place where the dialysis tube is inserted into the puncture opening to fix the dialysis tube, so that the dialysis tube can be more stably fixed, but the dressing may cause allergy when being attached to the skin for a long time, and the dressing has poor air permeability, so that local skin tissue fluid is easily exuded, and the phenomenon of soaking and whitening is caused.

In order to solve the problems in the prior art, the utility model discloses a dialysis tube fixing device, as shown in fig. 1, which comprises a limiting mechanism and a positioning mechanism 70, wherein the limiting mechanism can be worn on an arm of a patient and limits the bending angles of a big arm and a small arm, the positioning mechanism 70 is arranged on the limiting mechanism, a dialysis tube can be arranged in the positioning mechanism 70 in a penetrating manner, the positioning mechanism 70 can carry out vacuum adsorption on the dialysis tube so as to position the dialysis tube, the inner diameter of the dialysis tube can be prevented from being reduced while the dialysis tube is positioned, the larger blood flow in the dialysis tube can be ensured, and the smooth blood flow is ensured.

Referring to fig. 1 and 2, in a preferred embodiment, the limiting mechanism includes a first arm fixing plate 10, a second arm fixing plate 20 and an adjustable chuck 30, which are disposed in pairs, the first arm fixing plate 10 is connected to the second arm fixing plate 20 through the adjustable chuck 30, specifically, the adjustable chuck 30 includes a first arm 31 and a second arm 32 which can rotate relatively, and the first arm 31 and the second arm 32 are fixedly connected to the first arm fixing plate 10 and the second arm fixing plate 20 respectively.

In a preferred embodiment, one side of the oppositely disposed first arm fixing plate 10 is connected through an elastic band 60, the other side of the oppositely disposed first arm fixing plate 10 is connected through a velcro bandage with a sticking buckle, the oppositely disposed first arm fixing plate 10 is used for circumferentially clamping a large arm, and the velcro bandage with the sticking buckle can facilitate wearing and tightness adjustment of the first arm fixing plate 10.

In a preferred embodiment, one side of the oppositely disposed second arm fixing plate 20 is connected by an elastic band 60, and the other side of the oppositely disposed second arm fixing plate 20 is connected by a velcro bandage having a velcro, and the oppositely disposed second arm fixing plate 20 is used for circumferentially clamping the forearm.

In order to better adapt to the contours of the large arm and the small arm, the first arm fixing plate 10 and the second arm fixing plate 20 are arc-shaped plates, and the arc length of the first arm fixing plate 10 is greater than that of the second arm fixing plate 20.

In an alternative embodiment, the radians of the first arm fixing plate 10 and the second arm fixing plate 20 may be set to be two semicircles, so as to provide a larger clamping force to the arm and ensure the stability of limiting the bending of the arm.

In an alternative embodiment, the inner contours of the first arm fixing plate 10 and the second arm fixing plate 20 may also be configured to be matched with the outer contours of the arms through bionic modeling, so that the first arm fixing plate 10 and the second arm fixing plate 20 can be more matched with the arms of the patient, so as to provide greater limited stability.

It will be appreciated by those skilled in the art that in addition to nylon fleece strips with velcro, an adjustable connection may be achieved between adjacent first arm securing plates 10/second arm securing plates 20 with elastic bands 60 with buttons or snaps to facilitate patient wear.

Specifically, the first arm fixing plate 10 and the second arm fixing plate 20 provided in pairs are made of a rigid material to ensure sufficient supporting force to limit the large arm and the small arm.

In a preferred embodiment, as shown in fig. 3 and 4, the structure of the adjustment chuck includes an upper cover, a lower cover, a first gear 33, a second gear 34, a first shaft 35, a second shaft 36, a first shaft 37, a second shaft 38, a first arm 31, and a second arm 32; the first rotating shaft 35 and the second rotating shaft 36 are vertically disposed in the lower cover and are parallel to each other, the first gear 33 can rotate around the first rotating shaft 35, the second gear 34 is meshed with the first gear 33, the second gear 34 can rotate around the second rotating shaft 36, one end of the first transmission shaft 37 is fixedly connected to the upper portion of the first gear 33 and penetrates through the upper cover, the other end of the second transmission shaft 38 is fixedly connected to the lower portion of the first support arm 31, one end of the second transmission shaft 38 is fixedly connected to the upper portion of the second gear 34 and penetrates through the upper cover, the other end of the second transmission shaft 38 is fixedly connected to the lower portion of the second support arm 32, the first support arm 31 and the second support arm 32 are disposed on the outer side of the upper cover, and the second gear 34 can drive the second support arm 32 to rotate.

Since the first arm 31 is fixedly connected to the first arm fixing plate 10, and the second arm 32 is fixedly connected to the second arm fixing plate 20, when the first arm 31 and the first arm fixing plate 10 rotate, the first gear 33 rotates along with the first arm fixing plate, and the first gear 33 drives the second gear 34 to rotate, so that the second arm 32 and the second arm fixing plate 20 rotate.

In order to lock the relative angle between the first arm 31 and the second arm 32 to complete the limit of the bending angle of the arm, preferably, a spring 50 and a spring shaft pin 40 are further provided in the adjustment chuck, specifically, a spring 50 mounting hole is provided in the upper cover, the spring 50 is provided in the spring 50 mounting hole of the upper cover, the upper end of the spring shaft pin 40 penetrates through the upper cover, the middle part of the spring shaft pin 40 is fixedly connected with the bottom of the spring 50, the bottom of the spring shaft pin 40 can penetrate through the first gear 33, when the spring shaft pin 40 is lifted, the first gear 33 and the second gear 34 can rotate relatively, so that the first arm 31 and the second arm 32 can rotate relatively to each other, when the spring shaft pin 40 is released, the spring 50 drives the shaft pin to penetrate into the first gear 33 to block the rotation of the first gear 33, and at this time, the first gear 33 and the second gear 34 are locked relatively, and the first arm 31, the second arm 32, together with the first arm fixing plate 10 and the second arm fixing plate 20, realize the mutual locking.

As shown in fig. 5, in a preferred embodiment, the positioning mechanism 70 is fixedly connected to the outer side surface of the first arm fixing plate 10 and/or the second arm fixing plate 20, the positioning mechanism 70 is tubular, the length direction of the positioning mechanism 70 is parallel to the length direction of the first arm fixing plate 10 and/or the second arm fixing plate 20, the positioning mechanism 70 includes a rigid housing 71 and a flexible positioning portion 72, a vacuum exhaust valve 73 is provided on the rigid housing 71, a plurality of vacuum suction ports 721 are provided on the inner side wall of the flexible positioning portion 72, and the vacuum suction ports 721 are used for vacuum suction on the outer side wall of the dialysis tube.

In a preferred embodiment, the inner diameter of the flexible positioning portion 72 is adapted to the outer diameter of the dialysis tubing to ensure that the dialysis tubing can be threaded therethrough and can be adsorbed by the vacuum adsorption port 721 on the flexible positioning portion 72.

In a preferred embodiment, the rigid housing 71 is tubular in shape, and both ends of the rigid housing 71 extend circumferentially inward for fixing and supporting the flexible positioning portion 72 to prevent undesired displacement and deformation of the flexible positioning portion 72 when vacuum suction is performed.

In a preferred embodiment, the flexible positioning portion 72 has a cavity therein for vacuum suction, the outside of the flexible positioning portion 72 is connected to a vacuum exhaust valve 73, and the vacuum exhaust valve 73 is disposed on the outer surface of the rigid housing 71.

Specifically, the flexible positioning portion 72 is made of a rubber material or a silica gel material and has a solid structure at least in most areas, so as to avoid collapse during vacuum adsorption, one side of a cavity of the flexible positioning portion 72 is connected with the vacuum exhaust valve 73, the other side of the cavity is opened to form a vacuum adsorption port 721, and the vacuum exhaust valve 73 can be connected with a vacuum pump so as to realize negative pressure adsorption of the vacuum adsorption port 721 to the outer wall of the dialysis tube, so that the vacuum adsorption port 721 is positioned on the flexible positioning portion 72.

In a preferred embodiment, the vacuum suction port 721 is provided in an elongated shape along the axial direction of the flexible positioning portion 72; alternatively, the vacuum suction port 721 is provided in a circular ring shape along the circumferential direction of the flexible positioning portion 72.

In a preferred embodiment, the structure of the vacuum exhaust valve 73 can be referred to as the valve structure of the vacuum compression bag in the prior art, and its basic structure includes a valve cap, a valve core and a spring.

Specifically, the valve cover is generally a plastic cover, the inner side of the valve cover is provided with a protruding structure matched with the valve core, the outer side of the valve cover is provided with a protruding rotary knob, and the vacuum extraction valve can be opened or closed through the rotary knob. The valve core is generally configured in a cylindrical or conical shape, with a hole at the lower end thereof connected to the cavity of the flexible retainer 72 and a spring at the upper end thereof. When the rotary knob is opened, air enters the cavity of the flexible positioning portion 72 through the valve core hole, and when the rotary knob is closed, the valve core hole is sealed to prevent air from escaping outwards. The spring is a length of metal spring that connects the valve element and the valve cover and functions to return the valve element to the closed condition and maintain the vacuum within the cavity of the flexible retainer 72.

Those skilled in the art will appreciate that the vacuum exhaust valve 73 is a standard component, and can be purchased directly, and its structure is not improved, and its specific and tiny structural connection relationship will not be described in detail herein.

Further, the vacuum pump may be a hand-held automatic vacuum pump or a hand-operated vacuum pump, the automatic vacuum pump may be an H5A of elesspiri, the hand-operated vacuum pump may directly use a hand-held air pump, such as a hand-held air pump used in a compression bag, and the device can be purchased directly according to the requirement, and the structure thereof will not be described herein.

When the dialysis tube needs to be positioned, the dialysis tube only needs to penetrate into the flexible positioning part 72, then the vacuum exhaust valve 73 is connected and the vacuum pump is started, at the moment, the vacuum adsorption port 721 of the flexible positioning part 72 adsorbs the dialysis tube, the cavity of the flexible positioning part 72 forms a closed cavity, the adsorption stability of the dialysis tube is ensured, the dialysis tube is fixed in a clamping manner in the prior art, the inner diameter of the dialysis tube can be prevented from being reduced while the dialysis tube is positioned, the larger blood flow in the dialysis tube is ensured, and the smooth blood flow is ensured.

As a preferred solution, the first arm fixing plate 10 and/or the second arm fixing plate 20 are provided with at least two positioning mechanisms 70 side by side for fixing two arm branches of the dialysis tube respectively, and further, since the two arm branches form an included angle of 40 °, the two positioning mechanisms 70 side by side are preferably also disposed at a certain included angle so as to adapt to the two arm branches of the dialysis tube.

The use flow of the dialysis tube fixing device is as follows:

before dialysis, the patient can bend the arm to a comfortable angle, and the adjustable chuck 30 on the limiting mechanism can fix the arm to the angle so as to prevent the arm of the patient from being in disorder and thus cause the displacement of the dialysis tube, and further, the positioning mechanism 70 can fix the dialysis tube through vacuum adsorption, unlike the prior art which fixes the dialysis tube through clamping, can avoid reducing the inner diameter of the dialysis tube while positioning the dialysis tube, ensure that larger blood flow can be maintained in the dialysis tube, and ensure smooth blood flow.

The embodiments of the present utility model have been described above with reference to the accompanying drawings, but the present utility model is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present utility model and the scope of the claims, which are to be protected by the present utility model.

Claims

1. The dialysis tube fixing device is characterized by comprising a limiting mechanism and a positioning mechanism;

the limiting mechanism comprises a first arm fixing plate, a second arm fixing plate and an adjustable chuck which are arranged in pairs, wherein the adjustable chuck comprises a first support arm and a second support arm which can rotate relatively, the first support arm and the second support arm are respectively and fixedly connected with the first arm fixing plate and the second arm fixing plate, the adjacent first arm fixing plates and the adjacent second arm fixing plates are connected through elastic belts, the first arm fixing plates which are arranged relatively are used for circumferentially clamping a large arm, and the second arm fixing plates which are arranged relatively are used for circumferentially clamping a small arm;

the positioning mechanism is fixedly connected to the outer side face of the first arm fixing plate and/or the outer side face of the second arm fixing plate, the positioning mechanism is tubular, the length direction of the positioning mechanism is parallel to the length direction of the first arm fixing plate and/or the second arm fixing plate, the positioning mechanism comprises a rigid shell and a flexible positioning portion, a vacuum exhaust valve is arranged on the rigid shell, a plurality of vacuum adsorption ports are formed in the inner side wall of the flexible positioning portion, and the vacuum adsorption ports are used for carrying out vacuum adsorption on the outer side wall of the dialysis tube.

2. The dialysis tubing set according to claim 1, wherein the first arm mount and the second arm mount are each arcuate in shape, and wherein the arcuate length of the first arm mount is greater than the arcuate length of the second arm mount.

3. The dialysis tubing set according to claim 2, wherein one side of the oppositely disposed first arm fixing plates is connected by the elastic band, and the other side of the oppositely disposed first arm fixing plates is connected by a velcro bandage;

one side of the second arm fixing plate which is arranged oppositely is connected through the elastic band, and the other side of the second arm fixing plate which is arranged oppositely is connected through a nylon flannelette bandage with a sticking buckle.

4. The dialysis tubing set apparatus of claim 1, wherein the adjustment chuck comprises an upper cover, a lower cover, a first gear, a second gear, a first rotating shaft, a second rotating shaft, a first driving shaft, a second driving shaft, the first support arm, and the second support arm, wherein the first rotating shaft and the second rotating shaft are vertically disposed in the lower cover, the first gear can rotate around the first rotating shaft, the second gear is engaged with the first gear and connected, the second gear can rotate around the second rotating shaft, one end of the first driving shaft is fixedly connected to the upper portion of the first gear, the other end of the second driving shaft is fixedly connected to the lower portion of the first support arm, one end of the second driving shaft is fixedly connected to the upper portion of the second gear, the other end of the second driving shaft is fixedly connected to the lower portion of the second support arm, the first support arm and the second support arm are disposed on the outer side of the upper cover, and the second gear can drive the second support arm to rotate.

5. The dialysis tubing set apparatus of claim 4, further comprising a spring and a spring pin, wherein the spring is disposed in the upper cover, an upper end of the spring pin extends through the upper cover, a middle portion of the spring pin is fixedly connected to a bottom portion of the spring, and a bottom portion of the spring pin can extend through the first gear to lock the first gear.

6. The dialysis tubing securement device of claim 1, wherein the rigid housing is tubular, the ends of the rigid housing extending circumferentially inward, the flexible positioning portion having a cavity, the outer side of the flexible positioning portion being connected to the vacuum vent valve.

7. The dialysis tubing set according to claim 6, wherein the vacuum suction port is provided in an elongated shape along an axial direction of the flexible positioning portion;

or, the vacuum adsorption port is in a ring shape and is arranged along the circumferential direction of the flexible positioning part.

8. The dialysis tubing securement device of claim 6, wherein an inner diameter of the flexible positioning portion is adapted to an outer diameter of the dialysis tubing.

9. The dialysis tubing securement device of claim 6, wherein the flexible positioning portion comprises a rubber material or a silicone material.

10. The dialysis tubing set according to claim 1, wherein at least two of the positioning mechanisms are provided side by side on the first arm fixing plate and/or the second arm fixing plate.