JP7835405B2 - Prosthetic arm - Google Patents

Description

This invention relates to a prosthetic arm.

For example, when a part of the upper limb is lost due to an accident or illness, a prosthetic arm is used to compensate for the loss. Prosthetic arms are classified into several types: cosmetic prosthetics, which are solely for the purpose of restoring appearance; work prosthetics, which are specialized for specific tasks; and active prosthetics, which allow for arbitrary movements using other parts of the body via a harness or similar device. Of these, cosmetic prosthetics are incapable of performing any movements, and work prosthetics or active prosthetics are used when functional restoration is desired.

In active prosthetic limbs, maximizing the range of motion of the remaining joints is the most fundamental approach to improving user convenience.

Incidentally, in upper limb amputations, the most common are amputations or loss of fingers or palms. In cases of amputation or loss of the palm, joint motor function and sensory function are often preserved, offering various possibilities for functional reconstruction. Numerous cases of attempts to utilize the remaining function of the fingers have been reported, mainly by the Japanese Society for Surgery of the Hand and the Japanese Society for Microsurgery. Recent advances in surgical treatment have been remarkable, and in particular, in cases of amputation caused by sharp instruments, a high survival rate can now be achieved with reconstructive surgery to join the severed fragments.

On the other hand, in cases of severe amputation such as abrasion damage, reconstruction remains a long way off. Prosthetic limbs should be a viable option in such cases, but the technology for active prosthetics is lagging behind, and currently, it is largely unable to address a wide range of cases. Furthermore, functional improvement using prosthetic limbs is also desired in cases of congenital finger loss.

To address these issues, Patent Document 1 discloses a prosthetic hand having a pinching mechanism that includes a slider mechanism consisting of a slider axis and a slider, and which can perform a pinching motion by driving the thumb-side link and the four-finger-side link through abduction, adduction, and flexion/extension of the thumb CM joint.

Japanese Patent Publication No. 2015-146839

According to the prosthetic hand with a pinching mechanism disclosed in Patent Document 1, a pinching action can be performed by rotating and flexing the thumb CM joint toward the four fingers according to the intention of the person wearing the prosthetic hand, thereby driving the four fingers toward the thumb. However, because the pinching mechanism in Patent Document 1 is relatively large, it may be difficult to accommodate small hands, such as those of infants. Furthermore, since the pinching mechanism in Patent Document 1 is a sliding pair in which the slider shaft slides against the elongated hole of the slider, there is a risk of stiffness or wear due to friction, and countermeasures are necessary.

This invention has been made in view of the problems of the prior art, and aims to provide a small, highly efficient prosthetic hand.

To solve the above problems, one representative prosthetic hand of the present invention is a prosthetic hand that is attached to a hand with missing fingers,
The first bevel gear,
A first artificial finger extending radially with respect to the first bevel gear and rotating together with the first bevel gear,
A second bevel gear that meshes with the first bevel gear,
A second artificial finger extending radially with respect to the second bevel gear and rotating together with the second bevel gear,
The device has a shaft support portion that rotatably supports the first bevel gear and the second bevel gear, and a connecting mechanism that connects the second prosthetic finger and the remaining finger,
The flexion and extension movements of the finger are transmitted to the second prosthetic finger via the aforementioned connecting mechanism .

According to the present invention, it is possible to provide a small, highly efficient prosthetic hand.
Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments.

Figure 1 shows the prosthetic hand according to the first embodiment in a state where it is attached to the hand. Figure 2 is a diagram illustrating a model of a prosthetic arm according to the first embodiment. Figure 3 is a diagram illustrating the movement of the prosthetic arm, showing it from a side view. Figure 4 is a diagram illustrating the movement of the prosthetic arm, showing it from a frontal view. Figure 5 is a diagram similar to Figure 1, showing a prosthetic hand of the second embodiment.

(First embodiment)
The first embodiment of the present invention will be described in detail below.
Figure 1 shows the prosthetic hand 10 according to the first embodiment, attached to the hand HD. Note that the hand HD is assumed to have only the ring finger F4 and little finger F5 remaining. Both the ring finger F4 and little finger F5 are capable of flexion, extension, and abduction/adduction movements.

In Figure 1, the prosthetic hand 10 includes a socket 20, a drive device 30, a first prosthetic finger 41 corresponding to the thumb, a second prosthetic finger 42 corresponding to the index finger, a third prosthetic finger 43 corresponding to the middle finger, and a connecting mechanism 50. The second prosthetic finger 42 and the third prosthetic finger 43, which are parallel to each other, are connected at their bases and can move as a single unit. Also, as shown by the dotted line, a decorative cover member 60 made of silicone is provided to cover the first prosthetic finger 41, the second prosthetic finger 42, and the third prosthetic finger 43.

The socket 20 is, for example, a belt-shaped object wrapped around the palm of a hand HD, and serves as a support for the drive unit 30.

The drive unit 30 includes a single copper wire 31, a first bevel gear 32, and a second bevel gear 33.

The wire 31 is bent into a roughly U-shape, with both ends fixed to the socket 20 on the palm of the hand HD. The wire 31 also has a cylindrical first axial support portion 31a that extends straight toward the space between the first prosthetic finger 41 and the second prosthetic finger 42, and a cylindrical second axial support portion 31b that extends straight parallel to the bases of the second prosthetic finger 42 and the third prosthetic finger 43. By bending the wire 31 to form an acute angle, the first axial support portion 31a and the second axial support portion 31b are formed so as to sandwich the acute angle. By using the wire 31, the drive device 30 can be formed inexpensively and simply.

The first bevel gear 32 consists of a bevel gear portion 32a and a cylindrical support portion 32b, which are coaxially connected, and has a through hole 32c that penetrates them in the axial direction. The through hole 32c is rotatably fitted into the first shaft support portion 31a of the wire 31. In addition, an annular first locking portion 31c is attached to the first shaft support portion 31a near the support portion 32b, preventing the axial movement of the first bevel gear 32.

The support portion 32b is connected via the first connector 41a to the base of the first artificial finger 41, which extends radially from the first bevel gear 32, thereby enabling the support portion 32b and the first artificial finger 41 to rotate integrally.

The second bevel gear 33 consists of a bevel gear portion 33a and a cylindrical support portion 33b, which are coaxially connected, and has a through hole 33c that penetrates them in the axial direction. The through hole 33c is rotatably fitted into the second shaft support portion 31b of the wire 31. In addition, an annular second locking portion 31d is attached near the support portion 33b of the second shaft support portion 31b to prevent axial movement of the second bevel gear 33.

The support portion 33b is connected via the second connector 42a to the base of the second prosthetic finger 42, which extends radially from the second bevel gear 33. This allows the support portion 33b, the second prosthetic finger 42, and the third prosthetic finger 43 to rotate integrally.

The bevel gear portion 32a of the first bevel gear 32 and the bevel gear portion 33a of the second bevel gear 33 are meshed in a way that allows for power transmission. The axis X1 of the first bevel gear 32 and the axis X2 of the second bevel gear 33 intersect at an intersection angle θ. The intersection angle θ is less than 90 degrees, and preferably 60 to 80 degrees.

The connecting mechanism 50 includes a ring member 51 attached to the second joint of the ring finger F4, and a connecting member 52 that connects the outer circumference of the ring member 51 to the base of the third prosthetic finger 43.

Figure 2 is a diagram illustrating a model of the prosthetic hand 10 according to the first embodiment. As shown in Figure 2, the hand HD and the connecting mechanism 50 constitute an asymmetric four-bar linkage mechanism LK. The asymmetric four-bar linkage mechanism LK consists of the following four links.
(1) Link LK1: Connects the intersection (joint) J1 between the center of the ring finger F4 and the ring member 51, and the intersection (joint) J2 between the ring member 51 and the connecting member 52.
(2) Link LK2: Connects joint J2 to the intersection (joint) J3 between the second prosthetic finger 42 and the second connector 42a.
(3) Link LK3: Connects joint J3 and MP joint J4 of ring finger F4.
(4) Link LK4: Connects joint J4 and joint J1.

Joints J1 to J4 each pivotally connect two links. Link LK3 is composed of a part of the prosthetic hand 10 and the hand HD, and link LK4 is composed of the ring finger F4.

Figures 3 and 4 are diagrams illustrating the movement of the prosthetic arm 10.
First, when a person wearing the prosthetic hand 10 bends the ring finger F4 from the extended position shown in Figure 1, the force is transmitted to the third prosthetic finger 43 and the second prosthetic finger 42 via the ring member 51 and the connecting member 52, and the third prosthetic finger 43 and the second prosthetic finger 42 also flex toward the palm side of the hand HD in conjunction with the ring finger F4.

When the third prosthetic finger 43 and the second prosthetic finger 42 flex, the second bevel gear 33 rotates around the second shaft support 31b via the second connector 42a. As the second bevel gear 33 rotates, the first bevel gear 32, which meshes with it, rotates in the opposite direction around the first shaft support 31a. As a result, the first prosthetic finger 41 flexes toward the palm side of the hand HD via the first connector 41a. This operation is shown in Figure 3(a).

This flexion movement brings the tips of the second prosthetic finger 42 and the third prosthetic finger 43 closer to those of the first prosthetic finger 41, allowing objects to be grasped using these prosthetic fingers.

Conversely, when a person wearing the prosthetic hand 10 returns the ring finger F4 from a bent position to the extended position shown in Figure 1, force is transmitted in the opposite direction to that described above, causing the third prosthetic finger 43, the second prosthetic finger 42, and the first prosthetic finger 41 to extend so that their tips move apart from each other, allowing the person to release the object they are holding. This action is shown in Figure 3(b).

When picking up an object with the thumb and index finger, simply bringing the thumb and index finger together in a two-dimensional manner along the same plane may not be sufficient to grasp the object effectively. In contrast, according to this embodiment, by using a first bevel gear 32 and a second bevel gear 33 that mesh with each other, the first prosthetic finger 41, the second prosthetic finger 43, and the third prosthetic finger 43 can be made to move toward and apart from the object not in a straight line, but along intersecting planes. Such a mechanism is called an opposing rotation mechanism. By providing an opposing rotation mechanism in the prosthetic hand 10, the action of picking up an object can be easily achieved.

Furthermore, according to this embodiment, the flexion and extension movements of the remaining ring finger F4 allow the first prosthetic finger 41, the second prosthetic finger 42, and the third prosthetic finger 43 to be simultaneously flexed and extended. Therefore, even without the assistance of an actuator, the wearer of the prosthetic hand 10 can perform pinching movements arbitrarily according to their intentions. Clearly, if only the thumb and index finger are missing, the flexion and extension of the middle finger can be used to drive the first prosthetic finger 41 and the second prosthetic finger 42.

Furthermore, according to this embodiment, since power is transmitted using a rolling coupler consisting of a first bevel gear 32 and a second bevel gear 33, friction loss is reduced compared to a sliding coupler, enabling highly efficient operation and suppressing wear and tear on parts. In addition, because the drive unit 30 has fewer parts, a small and lightweight prosthetic arm 10 can be realized, making it particularly suitable for use by infants and the like. Moreover, by manufacturing the metal parts of the prosthetic arm 10 using materials such as stainless steel, the risk of corrosion can be suppressed, ensuring safety for the human body and contributing to environmental protection.

Furthermore, by modularizing the prosthetic hand 10 of this embodiment, it is possible to replace the movement of all missing fingers, not just the thumb. For example, by changing the shape of the second connector 42a, it can also accommodate cases where the ring finger or little finger is missing.

By the way, in the prosthetic hand 10 of this embodiment, in a simple flexion and extension movement of the ring finger F4, the first prosthetic finger 41, the second prosthetic finger 42, and the third prosthetic finger 43 move along the same trajectory, so the position of the second prosthetic finger 42 that the first prosthetic finger 41 contacts is always the same. For this reason, depending on the object being grasped, it may not be possible to grasp it properly. Therefore, in the prosthetic hand 10 of this embodiment, the position of contact of the first prosthetic finger 41 is made variable by utilizing the lateral movement of the ring finger F4.

Referring to Figure 2, the prosthetic hand 10 has an asymmetric four-bar linkage mechanism LK as described above. For example, when the ring finger F4, which constitutes link LK4, is brought close to the third prosthetic finger 43 in Figure 2, link LK4 rotates clockwise (in the direction of arrow A) around joint J4, and as a result joint J1 pushes link LK1 to the right, link LK2, which is connected via joint J2, rotates to the right. As a result, the second prosthetic finger 42 and the third prosthetic finger 43, which are connected to the connecting member 52, rotate clockwise (in the direction of arrow B) around joint J3. In other words, the lateral movement of the ring finger F4 is converted into rotational movement of the second prosthetic finger 42 and the third prosthetic finger 43.

When the ring finger F4 is bent while keeping it close to the third prosthetic finger 43, the first prosthetic finger 41 moves closer to the second prosthetic finger 42. This allows the first prosthetic finger 41 and the second prosthetic finger 42 to grasp an object. This action is shown in Figure 4(a).

In contrast, when the ring finger F4 is moved away from the third prosthetic finger 43 in Figure 2, the link LK4 rotates counterclockwise around the joint J4, and the second prosthetic finger 42 and the third prosthetic finger 43, which are connected to the connecting member 52, rotate counterclockwise around the joint J3.

Therefore, when the ring finger F4 is bent while keeping it away from the third prosthetic finger 43, the first prosthetic finger 41 moves closer to the third prosthetic finger 43. This allows the first prosthetic finger 41 and the third prosthetic finger 43 (or the three prosthetic fingers including the second prosthetic finger 42) to grasp an object. This action is shown in Figure 4(b).

The wearer of the prosthetic hand 10 can arbitrarily move the ring finger F4 and the third prosthetic finger 43 closer or further apart. This allows the first prosthetic finger 41 to be brought closer to any position between the second prosthetic finger 42 and the third prosthetic finger 43, enabling a pinching motion in accordance with the wearer's will. Furthermore, by adjusting the length and position of the connecting member 52, for example, the amount of rotational movement of the second prosthetic finger 42 and the third prosthetic finger 43 in relation to the lateral movement of the ring finger F4 can be finely adjusted.

(Second embodiment)
Figure 5 is a diagram similar to Figure 1, showing a prosthetic hand 10' of a second embodiment. The prosthetic hand 10' of this embodiment can be used when the ring finger F4 cannot be flexed or extended, or when the ring finger and little finger are also missing.

In this embodiment, the prosthetic arm 10' has an actuator 70 that rotates the first bevel gear 32, instead of providing a connecting mechanism 50. Furthermore, in order to connect the actuator 70 to the first bevel gear 32, the first shaft support portion 31a of the wire 31 terminates within the first bevel gear 32. The other configurations are the same as in the first embodiment, so redundant explanations are omitted.

According to this embodiment, by rotating the first bevel gear 32 in one direction via the actuator 70 in response to power supply from a power source (not shown), the first prosthetic finger 41 can be brought closer together with the second and third prosthetic fingers 42 and 43. Conversely, by rotating the first bevel gear 32 in the other direction, the first prosthetic finger 41 can be brought further apart with the second and third prosthetic fingers 42 and 43. The actuator 70 may be configured to rotationally drive the second bevel gear 33 instead of the first bevel gear 32.

10, 10': Prosthetic arm, 20: Socket, 30: Drive mechanism, 31: Wire, 32: First bevel gear, 33: Second bevel gear, 41: First prosthetic finger, 42: Second prosthetic finger, 43: Third prosthetic finger, 50: Connecting mechanism, 51: Ring member, 52: Connecting member, 60: Cover member, 70: Actuator, F4: Ring finger, F5: Little finger HD hand

Claims (2)

A prosthetic hand that is attached to a hand with missing fingers,
The first bevel gear,
A first artificial finger extending radially with respect to the first bevel gear and rotating together with the first bevel gear,
A second bevel gear that meshes with the first bevel gear,
A second artificial finger extending radially with respect to the second bevel gear and rotating together with the second bevel gear,
A shaft support portion that rotatably supports the first bevel gear and the second bevel gear,
The device has a connecting mechanism that connects the second prosthetic finger to the remaining finger,
The flexion and extension movements of the finger are transmitted to the second prosthetic finger via the aforementioned connecting mechanism.
A prosthetic arm characterized by the following features. The link mechanism includes the aforementioned connecting mechanism and the aforementioned fingers,
The lateral movement of the finger is converted into rotational movement of the second prosthetic finger via the link mechanism.
The prosthetic hand according to feature 1 .