Patent Description:
Along with the progress in medical science, minimally invasive surgery gains popularity in clinic treatment with advantages of smaller wounds, less pain and faster recovery. Specific mechanical arms are essential to performing the operation in a laparoscopic or thoracoscopic surgery.

In endoscopic surgeries, surgical instruments can only penetrate into the patient's body through a small incision of about <NUM> on the patient's body to perform complex surgical actions such as exploration, cutting, hemostasis and suturing, which put forward high requirements for mechanical arms with high degree of freedom. At present, the sophisticated minimally invasive surgical system represented by da Vinci surgical robot has high precision, high efficiency and powerful function, and both doctors and patients have good practical experience. However, due to the complex and bulky structure, expensive cost, complex procedure of operation and maintenance, the application range is limited. And additionally, the price of da Vinci surgical robot service is not acceptable for patients with limited economic conditions.

Therefore, various minimally invasive surgical mechanical arms have become the most convenient choice in the current minimally invasive surgery. The basic structure of the minimally invasive surgical mechanical arm, such as that disclosed in <CIT>, comprises a blade part, a blade joint assembly, a shaft and a handle. The blade part and the handle are respectively installed at the two ends of the shaft, controlling wires are disposed inside the shaft, and a joint assembly for controlling wire is disposed at the end near the handle so that the blade joint assembly at the other end can be controlled by the handle.

<CIT> discloses a surgical therapeutic instrument which includes an inserting part, a manipulating part, and a therapeutic part. In a link mechanism having a transmission shaft for transmitting a driving force applied to the manipulating part to the therapeutic part, the position of the transmission shaft is restricted, and a joint is provided in the transmission shaft to reduce the strain of the transmission shaft. A sheath is also provided in the inserting part to facilitate cleaning thereof. A mechanism is provided for immovably locking the movable portion. A circular arc centered about a turning shaft is introduced into the shape of the manipulating part to improve the manipulability thereof. Further, the structure of a gripping portion of the manipulating part is improved.

Degrees of freedom of the prior mechanical arms are limited, the flexibility of the blade joint assembly is not satisfying which makes the operation inefficient. And as the handle is coaxial with the shaft, the operation posture is inconsistent with the requirements of ergonomics which causes fatigue to the user. Such limitation has negative effects on the efficiency and safety of the operation.

The objective of the invention is to provide a portable minimally invasive surgical mechanical arm with multi-degree of freedom, the blade part of which can swing and rotate freely, simplifying the operation and improving the ergonomics.

The invention is related to a portable minimally invasive surgical mechanical arm with multi-degree of freedom as defined in claim <NUM>. Embodiments of the invention are recited in the dependent claims.

A portable minimally invasive surgical mechanical arm with multi-degree of freedom comprises a blade part, a blade joint assembly, a shaft and a handle. The blade part is installed at one end of the shaft by the blade joint assembly, and the handle is installed at the other end of the shaft. The shaft comprises a plurality of controlling wires and a controlling wire joint assembly arranged at the other end. The controlling wire joint assembly and the blade joint assembly are connected by the plurality of controlling wires. The handle comprises a grip part, a handle joint assembly and a controlling mechanism. The grip part comprises a grip portion and an axle part. The axle part is movably connected to the handle joint assembly and the handle joint assembly comprises a first axis and a second axis that are mutually perpendicular to each other allowing the axle part to rotate around the first axis and the second axis respectively, wherein the first axis coincides with the axis of the axle part, and the second axis is perpendicular to the shaft. The controlling mechanism connects the axle part and the controlling wire joint assembly, and is used for transferring the movement of the handle to the controlling wire joint assembly. The controlling mechanism comprises a four-link mechanism, and the four-link mechanism comprises an input piece, two push rods and an output piece, and the two push rods are connected with the input piece and the output piece respectively, with the input piece receiving movements of the axle part and the output piece being a part of the controlling wire joint assembly.

Preferably, the grip part is set on one side of the shaft, so that a holding direction of the grip part is intersected with an axial direction of the shaft.

The user can grasp and operate the mechanical arm with a more natural gesture, so that it is flexible and convenient to operate the mechanical arm and the ergonomics can be improved. The user can control the blade joint assembly by moving the wrist of the holding hand, dispense with double-hand operating and simplifying the operation method.

Preferably, the grip part also comprises a shell fixedly installed with respect to the shaft, and the shell accommodates the handle joint assembly and the controlling mechanism. The handle joint assembly comprises an inner cylinder with the first axis as an axis, the inner cylinder is nested in the shell, and the inner cylinder can rotate around its own axis relative to the shell. The axle part is connected to the inner cylinder with a pivot and is axially aligned with the inner cylinder; and the pivot is arranged along the second axis.

Preferably, the grip part also comprises a shell fixed to the shaft, and the shell accommodates the handle joint assembly and the controlling mechanism. The handle joint assembly comprises an inner cylinder and an outer cylinder with the first axis as an axis, and the axle part is set in the inner cylinder being rotatable around its own axis relative to the outer cylinder, and the outer cylinder is connected to the shell with a pivot, and the pivot is arranged along the second axis.

Preferably, the handle also comprises a shell fixed to the shaft and the shell accommodates the handle joint assembly and the controlling mechanism. The handle joint assembly is a ball joint including a joint ball and a support socket, and the joint ball is set at the end nearer to the shaft of the axle part, while the support socket is fixed on the shell, and an axis of an opening of the support socket is the first axis.

Preferably, the controlling wire joint assembly comprises a third axis and a fourth axis perpendicular to each other, allowing the controlling wire joint assembly to rotate in the same direction with the axle part to drive the controlling wires, so that the blade joint assembly is driven to bend. Because of the controlling wire joint assembly, the blade joint assembly bend in the direction same with the user's wrist gesture which is customary to the operation habit in the operation.

Preferably, the input piece of the four-link mechanism is a push-rod-plate, and the center of the push-rod-plate is on the first axis, and the push-rod-plate is pivotedly connected with the axle part in the direction parallel to the second axis. In operation, the push-rod-plate can rotate around the first axis, which makes the controlling mechanism small and compact. The bending moment of the push rods is reduced due to the pivoted connection with the axle part improving the service life of the part.

Preferably, the handle comprises a locking system, and the locking system comprises a locking switch, a locking transmission and a brake. The locking switch is located on the grip part, and the locking switch is connected to one end of the locking transmission while the brake is connected to the other end of the locking transmission. The locking switch has two states of locking and releasing, and when the locking switch is in the state of locking, the locking transmission drives the brake to a locking position to lock the handle joint assembly or the input piece of the four-link mechanism, so that the four-link mechanism is frozen; and when the locking switch is in the state of releasing, the brake moves out of the locking position leaving the input piece movable. The blade joint assembly can be locked by the locking system in operation so that the blade part is in a fixed position improving the operation safety.

Preferably, the handle comprises a blade switch rod and a blade controlling wire, and the blade switch rod is connected with the blade part through the blade controlling wire to make the blade part open or close. The blade switch rod is installed on the grip part. The blade switch rod and the grip part are arranged in the shape of herringbone, so that a user can pull the blade switch rod with fingers when holding the grip portion in hand. The handle also comprises a blade rotating knob, and the blade rotating knob is connected with the blade part through an elastic rod for controlling the blade part rotating around its axis. The blade rotating knob is installed on the grip part and is set in an upper location to the blade switch rod allowing a user to turn the blade rotating knob with an index finger when holding the grip portion. The user can hold the handle and make the mechanical arm perform bending, rotating, locking and making the blade part open or close with one hand, avoiding double-hand operating, simplifying the operation, and improving the efficiency of surgeries.

Optionally, the blade part comprises electrosurgical instruments, and both of the shaft and the handle contain power lines for the electrosurgical instruments. The handle comprises an electrosurgical instrument switch, which is adjacent to the blade rotating knob allowing a user to operate the electrosurgical instrument switch with an index finger when holding the grip portion.

Preferably, the axle part is hollow allowing the blade controlling wire and the elastic rod extend through the axle part. The hollow axle part compacts the handle, optimizes the volume and reduces the weight.

Optionally, the shaft comprises a straight segment and a bending segment, and the straight segment and the handle are connected by the bending segment with the grip part of the handle located on an extension cord of the straight segment. The bending segment allows the relative position of the handle and the knife head to be adjusted according to the actual use scenario, making the operation more flexible.

Previous figures are presented for a fuller understanding of the nature and design objects rather than as restriction for embodiments of the present invention. Wherein the x, y, z are coordinate system set for better illustrating the spatial relationship in the figures. The meanings of the signs and coordinate systems in each Fig. remain consistent. The previous figures are schematic illustration of the embodiments rather than accurate drawings including all the details of the parts.

Further detailed description shall be made by the following embodiments in conjunction with the drawings.

<FIG> is a schematic view showing the structure of a portable minimally invasive surgical mechanical arm with multi-degrees of freedom. The blade part <NUM> is connected to one end of the shaft <NUM> through the blade joint assembly <NUM>, and the other end of the shaft <NUM> is connected to the handle <NUM>. The handle <NUM> comprises a shell <NUM>, a controlling mechanism <NUM> and a grip part <NUM>. The shell <NUM> is fixed with the shaft <NUM>, and the controlling mechanism <NUM> is installed inside the shell <NUM>. According to <FIG>, one end of the grip part <NUM> is the axle part <NUM>, and the axle part <NUM> is inserted into the shell <NUM>. The user holds the other end of the grip part <NUM>, namely a grip portion, to operate the mechanical arm. When the user holds the grip part <NUM>, the thumb is positively oriented towards the z-axis relative to the palm, and this direction is defined as the holding direction.

As shown in <FIG> and <FIG>, a handle joint assembly is installed inside the shell <NUM>, wherein the handle joint assembly comprises an outer cylinder <NUM>, an inner cylinder <NUM> and a pivot <NUM> with a second axis. The inner cylinder <NUM> can rotate around the first axis <NUM> in the z-axis direction relative to the outer cylinder <NUM>, and the axial direction of the pivot <NUM> with the second axis is the second axis. The axle part <NUM> is connected with the inner cylinder <NUM> through the second rotating axis pivot <NUM>, and the axle part <NUM> can rotate around the second axis through the pivot <NUM> with the second axis. A fulcrum rod <NUM> is fixed on the axle part <NUM>, and it is connected with the controlling mechanism <NUM>. The controlling mechanism <NUM> comprises a push-rod-plate <NUM> and two push rods <NUM>, the push-rod-plate <NUM> is pivotedly connected with the fulcrum rod <NUM>, allowing the push-rod-plate <NUM> to rotate around the y-axis relative to the fulcrum rod <NUM>, and the position of the connection point is on the first axis <NUM>. According to <FIG>, the two push rods <NUM> are pivotedly connected with the controlling wire joint assembly <NUM>, and the push-rod-plate <NUM>, the push rods <NUM> and the controlling wire joint assembly <NUM> form a four-link mechanism with the push-rod-plate <NUM> being an input piece receiving the movement input by the fulcrum rod <NUM> and driving the controlling wire joint assembly <NUM>. The fulcrum rod <NUM> and the push rods <NUM> are rods with some flexibility.

The structure of the controlling wire joint assembly <NUM> is shown in <FIG>, it comprises two pivots, and one of the pivots is arranged on the third axis <NUM> and the other of the pivot is arranged on the fourth axis <NUM> of the controlling wire joint, so that the controlling wire joint assembly <NUM> can rotate around the third axis <NUM> and the fourth axis <NUM> respectively. According to <FIG>, the two push rods <NUM> are pivotedly connected to the controlling wire joint assembly and installation position is above the fourth axis <NUM>. One end of multiple controlling wires <NUM> is fixed on the controlling wire joint assembly <NUM>, and the other end is fixed on the blade joint assembly2 (including the case that the controlling wires directly fixed on the blade part <NUM>).

When the mechanical arm is utilized in operation, the shaft <NUM> is inserted into the patient's body through a surgical incision, and its position is relatively fixed. The user holds the grip part <NUM> with one hand, makes the axle part <NUM> rotate by moving the wrist of the holding hand, so that the bending blade joint assembly drives the blade part towards a direction required by surgical operation.

<FIG> is a schematic view of the blade part <NUM> swinging in the xz-plane. When the blade part <NUM> is required to swing towards the negative direction of the z-axis, the grip part <NUM> is made to rotate counterclockwise around the second axis <NUM> according to the direction of the arrow, so that the blade joint assembly <NUM> is driven to bend to the negative direction of the z axis by the controlling mechanism <NUM>. The movement of the controlling mechanism <NUM> can be demonstrated in combination with <FIG>, where the grip part <NUM> rotates counterclockwise around the pivot <NUM> with the second axis along the direction of the arrow, driving the fulcrum rod <NUM> and the push-rod-plate <NUM> to move together, and the push-rod-plate <NUM> drives the push rods <NUM> to move forward in the positive direction of the x-axis, and pushes the controlling wire joint assembly <NUM> to rotate counterclockwise around the fourth axis <NUM> of the controlling wire joint assembly. At this time, the upper controlling wire <NUM> is relaxed, and the lower controlling wire <NUM> is tightened, thus driving the blade joint assembly <NUM> to bend towards the negative direction of the z-axis. The stopper <NUM> plays a restricting role in the movement range of the push-rod-plate <NUM>, to avoid its movement exceeding the acceptable range of the controlling wire joint assembly <NUM>.

As the fulcrum rod <NUM> and the push rods <NUM> are flexible rods, the motion component, which generated by the push-rod-plate <NUM> following the fulcrum rod <NUM> rotating around the pivot <NUM> with the second axis in the z-axis direction, can be absorbed by the elastic deformation of the fulcrum rod <NUM> and the push rods <NUM>, reducing the stress of the hinge structure; the push-rod-plate <NUM> is pivotedly connected with the fulcrum rod <NUM>, and can rotate around the y-axis, eliminating the angle change caused by the rotation of the fulcrum rod <NUM>, so that the push-rod-plate <NUM> is always parallel to the xy-plane, optimizing the stress state of the fulcrum rod <NUM> and the push-rod-plate <NUM>. As a result, the service life of the relevant parts are prolonged and the reliability of the mechanical arm is improved.

<FIG> is a schematic view of blade part <NUM> swinging towards the negative direction of y-axis. When the blade part <NUM> is required to swing towards the negative direction of the y-axis as shown in <FIG>, as <FIG> illustrates that the axle part <NUM> rotates clockwise around the first axis <NUM> according to the direction of the arrow, and the controlling wire joint assembly <NUM> is driven to the right by the controlling mechanism <NUM>. As shown in <FIG>, the push-rod-plate <NUM> is driven by the axle part <NUM> to rotate clockwise around the first axis <NUM>, so that the controlling wire joint assembly <NUM> is driven to rotate clockwise around the third axis <NUM> of the controlling wire joint assembly by the two push rods <NUM>. During this process, the controlling wires <NUM> on the left are relaxed and the controlling wires <NUM> on the right are tightened, so that the blade joint assembly <NUM> is bent towards the negative direction of the y axis.

As shown in <FIG> and <FIG>, the handle <NUM> comprises a locking system including a locking switch <NUM>, a locking transmission <NUM>, a brake <NUM> and an elastic restorer <NUM>. The locking transmission <NUM> is a locking controlling wire, one end of which is connected with the locking switch <NUM> and the other end is connected with the brake <NUM>, and the brake is connected to the shell <NUM> through the elastic restorer <NUM>. As shown in <FIG>, when the blade joint assembly is bent to the predetermined position, the locking switch <NUM> is turned to the locking position, and the locking transmission <NUM> is driven to bring the brake <NUM> to press the push-rod-plate <NUM>, so that the push-rod-plate <NUM> is prevented from moving, locking the blade joint assembly. When the locking switch <NUM> is turned to the releasing position, the locking transmission <NUM> is relaxed, and the brake <NUM> moves away from the push-rod-plate <NUM> under the drive of the elastic restorer <NUM>, and the blade joint assembly is unlocked. The brake <NUM> is a friction plate, and the elastic restorer <NUM> is a reed or spring shaft. When the locking switch <NUM> is in the locking position, the brake <NUM> swings in the negative direction of the z-axis and presses the push-rod-plate <NUM> together with the stopper <NUM>, so that the push-rod-plate <NUM> is locked by the friction. When the locking switch <NUM> is in the releasing position, the brake <NUM> swings in the positive direction of the z-axis and moves away from the push-rod-plate <NUM> under the elastic force of the elastic restorer <NUM>, so as to restore the freedom of movement of the push-rod-plate.

In another embodiment, as shown in <FIG>, the push-rod-plate <NUM> is replaced by a "Y" shaped fork arm. One end of the fork arm is pivotedly connected with the fulcrum rod <NUM>, so that the fork arm can rotate around the y-axis direction relative to the fulcrum rod <NUM>. The other end is pivotedly connected with two push rods <NUM>, and the fork arm can rotate around the first axis <NUM> driven by the fulcrum rod <NUM>. The brake <NUM> is configured as a brake caliper. When the locking switch <NUM> is in the locking position, the fork arm is clamped by the brake caliper and is immovable. When the locking switch <NUM> is in the releasing position, the brake caliper frees the fork arm, so as to restore the movability of the folk arm.

In another embodiment, an electrosurgical instrument is integrated to the blade part <NUM>, the electrosurgical instrument can be a high-frequency electrotome, an ultrasonic knife or an argon gas knife. As shown in <FIG>, the handle <NUM> is equipped with a power line <NUM> and an electrosurgical instrument switch <NUM>, which are used to power and control the electrosurgical instrument.

The handle <NUM> is equipped with a blade switch rod <NUM> and a blade rotating knob <NUM>. As shown in <FIG>, blade controlling wire <NUM> passes through the shaft <NUM>, one end of which is connected with the blade part <NUM> and the other end is connected with the blade switch rod <NUM>. In operation, the blade switch rod <NUM> can be pulled to drive the blade controlling wire <NUM> to open or close the blade part <NUM>. The blade rotating knob <NUM> connects with the blade part through an elastic rod <NUM>, and the blade rotating knob <NUM> can drive the blade part to rotate around the x axis. The blade switch rod <NUM> and the grip portion of the grip part <NUM> are arranged in a herringbone pattern, so that the user can hold the grip part <NUM> with the palm against the grip portion, and pull the blade switch rod <NUM> with fingers, to open or close the blade part <NUM>. The blade rotating knob <NUM> is set in a upper location above the blade switch rod <NUM>, so that the user can turn the blade rotating knob <NUM> with the index finger to make the blade part <NUM> to rotate around the x axis. The locking switch <NUM> is arranged on the side of the grip part <NUM>, so that the user can turn the locking switch to lock blade joint assembly <NUM> with the thumb. The electrosurgical instrument switch <NUM> is arranged under the blade rotating knob <NUM>, so that the user can operate the electrosurgical instrument with the index finger when holding the grip part <NUM>. Depending on the kind of the electrosurgical instruments integrated by the knife head <NUM>, the operations include high frequency electric cutting, electric coagulation, ultrasonic cutting, ultrasonic coagulation, argon plasma coagulation or other surgical actions.

As shown in <FIG>, when the pivot <NUM> with the second axis rotates around the first axis <NUM> with the axle part <NUM> and is unparalleled to the y axis and the fourth axis <NUM> of the of the controlling wire joint assembly. In this case, the user holds the grip part <NUM> and rotates around the with the second axis <NUM>. As shown in <FIG>, the push-rod-plate <NUM> produces a motion component in the y-axis direction. Additional bending moments borne by the fulcrum rod <NUM> and the push rods <NUM> maintains the movement of the four-link mechanism consisting of the push-rod-plate <NUM>, push rods <NUM> and the controlling wire joint assembly <NUM>.

This situation can be optimized by a preferable embodiment illustrated by <FIG>: the inner cylinder <NUM> of the grip part joint assembly is directly installed on the axle part <NUM> and nested with the outer cylinder <NUM>, and the axle part <NUM> can rotate around the first axis <NUM> relative to the outer cylinder <NUM>. The outer cylinder <NUM> with the first axis is connected with the shell through the pivot <NUM> with the second axis, so that the axle part <NUM>, the inner cylinder <NUM> and the outer cylinder <NUM> can rotate around the pivot <NUM> with the second axis.

When the grip part <NUM> rotates around the pivot <NUM> with the second axis, the outer cylinder is driven to rotate together; when the grip part <NUM> rotates around the first axis <NUM>, the parallel relationship between the pivot <NUM> with the second axis and the y-axis is remained, thereby ensuring that the pivot <NUM> with the second axis is always paralleled with the fourth axis <NUM> of the controlling wire joint assembly. So that interference between the grip part <NUM> rotating around the first axis <NUM> and the grip part <NUM> rotating around the pivot <NUM> with the second axis is eliminated, reducing the additional stress on the controlling mechanism caused by the combined movements of grip part <NUM> simultaneously rotating around the first axis <NUM> and around the pivot <NUM> with the second axis, improving the service life of the parts and optimizing the smoothness of the bending movement of the blade joint assembly <NUM>.

In another embodiment, as shown in <FIG>, the handle joint assembly is a ball joint, comprising the joint ball <NUM> and the support socket <NUM>, the joint ball <NUM> is arranged on the top of the axle part <NUM>, and the fulcrum rod <NUM> is connected with the joint ball <NUM>. The axis of the opening of the support socket <NUM> is the first axis <NUM>, and the axis parallels to the y axis of the joint ball is the second axis. Ball joint allows the grip part to rotate around the first axis <NUM> and swing in the xz-plane. A brake window <NUM> is arranged on the joint ball <NUM>, and a rubber brake pad <NUM> is arranged on the inner side of the support socket <NUM> corresponding to the brake window <NUM>. The locking switch <NUM> is connected with the brake <NUM> with a rubber pressing part through the locking transmission part <NUM>. The locking transmission part 21is a lever fixed on the brake pivot <NUM>. When the locking switch <NUM> is turned, the handle, locking transmission <NUM>, rotates around the brake pivot <NUM>, driving the brake <NUM> pass through the brake window <NUM> and press the brake pad <NUM>, so that the joint ball <NUM> is locked by the friction and cannot rotate relative to the support socket <NUM>, and braking is achieved. The ball joint can reduce the parts of the handle joint assembly, simplifying manufacturing and maintenance.

Preferably, the support socket <NUM> is provided with a positioner, so that the joint ball can only rotate around the z axis and the y axis, but cannot rotate around the x axis, so as to reduce the additional moment borne by the fulcrum rod <NUM>, and improve the reliability of the parts.

Preferably, the brake pivot <NUM> is provided with a spring shaft. When the locking switch <NUM> is turned to the releasing position, the elasticity of the spring shaft boosts the rotation of the lever <NUM>, so that the brake <NUM> and the brake pad <NUM> can be rapidly separated, improving the agility of the brake termination process of mechanical arm, and optimizing the effectiveness of the operation.

In another embodiment, a rubber brake piece is arranged on the outside of the joint ball <NUM>. One end of the locking transmission <NUM> is connected with the brake switch <NUM>, and the other end is connected with a brake rod installed in the support socket <NUM>. The brake rod is provided with a rubber pressing part that fits the arc surface of the joint ball. When the brake switch <NUM> is pulled, the locking transmission <NUM> drives the brake rod to press the brake piece from the outside of the joint ball <NUM>. The joint ball <NUM> is prevent from rotating relative to the support socket <NUM> by the friction, achieving the braking. The pressing part of the brake rod is arranged on the outside of the joint ball <NUM>, improving the contact area that contributes to the friction, and achieving braking more effectively.

In another embodiment, as shown in <FIG>, there is a bending segment <NUM> on the shaft <NUM>, so that the blade part <NUM> and the upper end of the grip part <NUM> are in the same axis, thus the operation of the mechanical arm matches operation habits of laparoscopic instruments.

Claim 1:
A portable minimally invasive surgical mechanical arm with multi-degree of freedom comprising a blade part (<NUM>), a blade joint assembly (<NUM>), a shaft (<NUM>) and a handle (<NUM>);
wherein the blade part (<NUM>) is installed at one end of the shaft (<NUM>) by the blade joint assembly (<NUM>), and the handle (<NUM>) is installed at the other end of the shaft (<NUM>);
the shaft (<NUM>) comprises a plurality of controlling wires (<NUM>) and a controlling wire joint assembly (<NUM>) at the other end of the shaft (<NUM>);
the controlling wire joint assembly (<NUM>) and the blade joint assembly (<NUM>) are connected by the plurality of controlling wires (<NUM>);
wherein the handle (<NUM>) comprises
a grip part (<NUM>) comprising a grip portion and an axle part (<NUM>), wherein the grip portion is used for holding;
a handle joint assembly which is used to movably connect the axle part (<NUM>); and
a controlling mechanism (<NUM>) connecting with the axle part (<NUM>) and the controlling wire joint assembly (<NUM>), and used for transferring the movement of the grip part (<NUM>) to the controlling wire joint assembly (<NUM>);
the portable minimally invasive surgical mechanical arm being characterized in that
the controlling mechanism (<NUM>)comprises a first axis (<NUM>) and a second axis that are mutually perpendicular to each other, and allows the axle part (<NUM>) to rotate around the first axis (<NUM>) and the second axis respectively, wherein the first axis (<NUM>) coincides with an axis of the axle part (<NUM>) and the second axis is perpendicular to the shaft (<NUM>); and
and the controlling mechanism (<NUM>) comprising a four-link mechanism;
wherein the four-link mechanism comprises an input piece (<NUM>), two push rods (<NUM>) and an output piece, and the two push rods (<NUM>) are connected with the input piece (<NUM>) and the output piece, the input piece (<NUM>) is configured for receiving movements of the axle part (<NUM>) and the output piece is a part of the controlling wire joint assembly (<NUM>).