Link mechanism and prosthetic hand using same

Abstract

Provided are: a link mechanism that is suitable for use in prosthetic hands and the like due to being low cost and having a simple structure; and a prosthetic hand using the same. A link mechanism comprises: a first joint part that includes a first link (110 (A)) and a second link (110 (B)) connected to the first link so as to be rotatable about a first base axis (AX1); a second joint part that is arranged side-by-side with the first joint part and includes a third link (110 (D)) and a fourth link (110 (E)) connected to the third link so as to be rotatable about a second base axis (AX2) which is different from the first base axis, wherein the third link is connected to the second link so as to be rotatable about a third base axis (AX3) which is different from the first base axis and the second base axis.

Description

Link mechanism and prosthetic hand using the same

[0001] The present invention relates to a link mechanism and a prosthetic hand using the same.

[0002] For those with congenital or acquired defects or malformations of the palm due to congenital causes or accidents, etc., a prosthetic hand equipped with a hand tip device that restores the form and function of the hand is worn.

[0003] For example, in Patent Document 1, a finger drive unit of an electric prosthetic hand is disclosed, which includes a piston that moves forward and backward by a feed screw that rotates through a reduction gear with the rotation of a motor, a middle joint member that is connected to a base joint member that rotates in response to the movement of the piston, and a distal joint member that is connected to the middle joint member. When the base joint member rotates, the first sliding contact portion of the base joint member can bend a first wire member installed between the middle joint member and the main body into a U shape.

[0004] Japanese Patent Application Laid-Open No. 2021-130049

[0005] The prosthetic hand of Patent Document 1 has problems such as a relatively large number of parts, a complex structure, and high costs. Therefore, there is a demand to realize a prosthetic hand with a simpler structure and cost reduction.

[0006] The present invention has been made in view of such problems of the prior art, and an object thereof is to provide a link mechanism that is suitable for, for example, a prosthetic hand because it is low-cost and simple, and a prosthetic hand using the same.

[0007] To achieve the above object, one of the representative link mechanisms of the present invention includes a first joint portion including a first link and a second link rotatably connected to the first link about a first axis, a third link, and a fourth link rotatably connected to the third link about a second axis different from the first axis, and has a second joint portion parallel to the first joint portion. The third link is rotatably connected to the second link about a third axis different from the first axis and the second axis.

[0008] According to the present invention, a link mechanism and a prosthetic hand using the same can be provided, which are suitable for prosthetic hands, for example, because they are low-cost and simple. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

[0009] Figure 1 is a perspective view showing the flexion and extension movement of a prosthetic finger including a link mechanism according to the first embodiment. Figure 2 is a perspective view showing the flexion and extension movement of a prosthetic finger including a link mechanism according to the first embodiment. Figure 3 is a perspective view showing the flexion and extension movement of a prosthetic finger including a link mechanism according to the first embodiment. Figure 4 is a perspective view showing the flexion and extension movement of a prosthetic finger including a link mechanism according to the first embodiment. Figure 5 is a diagram showing the link plate, which is an element of the link mechanism, in a connected state. Figure 6 is a perspective view of the prosthetic finger including a link mechanism according to the second embodiment, attached to the wearer's hand and viewed from the back of the hand. Figure 7 is a view of the prosthetic finger including a link mechanism according to the second embodiment, attached to the wearer's hand and viewed from the palm side. Figure 8 is a perspective view showing the flexion and extension movement of a prosthetic finger according to the second embodiment. Figure 9 is a perspective view showing the flexion and extension movement of a prosthetic finger according to the second embodiment. Figure 10 is a perspective view showing the flexion and extension movement of a prosthetic finger according to the second embodiment. Figure 11 is a perspective view showing a modified version of the second embodiment of the link mechanism. Figure 12 is a perspective view of the link mechanism according to the third embodiment. Figure 13 is a perspective view of the link mechanism according to the fourth embodiment. Figure 14 is a side view of the link mechanism according to the fifth embodiment. Figure 15 is a perspective view showing a part of the link mechanism according to the fifth embodiment. Figure 16 is a diagram illustrating an example of a specification change in the fifth embodiment. Figure 17 is a diagram illustrating an example of a specification change in the fifth embodiment.

[0010] The link mechanism of the present invention will be described below with reference to the drawings.

[0011] (First Embodiment) Figures 1 to 4 are perspective views showing the flexion and extension movement of a prosthetic finger FG including a link mechanism 100 according to the first embodiment. Figure 5 is a diagram showing a link plate (also simply called a link), which is an element of the link mechanism 100, and here shows a state in which four link plates 110 are connected to each other.

[0012] In Figures 1 to 4, the prosthetic finger FG comprises a link mechanism 100, an actuator 150, and a fingertip member 160. When the prosthetic finger FG is used as part of a prosthetic hand, the actuator 150 can be attached, for example, to the back of the wearer's hand.

[0013] The actuator 150 includes a case 151, a motor 152 mounted on the case 151, a pivot member 153 (Figures 2 and 3) that can pivot relative to the case 151, a fixing plate 154 fixed to the case 151, and a reduction mechanism (not shown) disposed inside the case 151. The case 151 and the fixing plate 154 constitute the base end. The motor 152 is powered by a power source (not shown) and generates driving force. The driving force of the motor 152 is reduced by the reduction mechanism and transmitted to the pivot member 153, causing the pivot member 153 to pivot.

[0014] A pivot pin 155 is embedded in the end of the pivot member 153. The pivot pin 155 fits into a hole 156a of the drive member 156, and the pivot pin 155 and the hole 156a are rotatable relative to each other. In addition, a fixing pin 157 is embedded in the fixing plate 154.

[0015] The link mechanism 100 has a plurality (five in this case) of link plates 110 having a common shape and thickness. As shown in Figure 5, the link plates 110 are elongated plates, with one end formed into a roughly triangular portion. Here, the end with the roughly triangular portion is called the wide end, and the end opposite the wide end is called the narrow end.

[0016] The link plate 110 has a first hole 111, a second hole 112, and a third hole 113, which are preferably circular in shape and have the same diameter. The first hole 111 is formed at the narrow end, the second hole 112 is formed at the wide end, and the third hole 113 is formed in the wide end at a position where its axis (axis of rotation) is shifted with respect to the plane containing the axes (axis of rotation) of the first hole 111 and the second hole 112.

[0017] The link plates 110 are arranged in two parallel rows in series. In Figures 1 to 4, the link plates 110 in the first row (first joint) are all connected in series with their wide ends facing the actuator 150, and for identification purposes, they are designated 110(A), 110(B), and 110(C) starting from the side closest to the actuator 150. In contrast, the link plates 110 in the second row (second joint), which are parallel to the first row, are all connected in series with their narrow ends facing the actuator 150, and for identification purposes, they are designated 110(D) and 110(E) starting from the side closest to the actuator 150. Link plate 110(A) constitutes the first link, link plate 110(B) constitutes the second link, link plate 110(D) constitutes the third link, link plate 110(E) constitutes the fourth link, and link plate 110(C) constitutes the fifth link.

[0018] As shown in Figure 3, the second hole 112 of the link plate 110(A) is fitted onto the fixing pin 158 planted in the case 151, and is rotatably connected to the fixing pin 158. The first hole 111 of the link plate 110(A) and the second hole 112 of the link plate 110(B) are fitted onto the pin 121, and are rotatably connected relative to it. Also, the first hole 111 of the link plate 110(B) and the second hole 112 of the link plate 110(C) are fitted onto the pin 122, and are rotatably connected relative to it. A fingertip member 160 is attached to the link plate 110(C). The rotation axes of the fixing pin 158, pins 121 and 122 are parallel, with the rotation axis of pin 121 being the first base axis AX1 (Figure 5) and the rotation axis of pin 122 being the fourth base axis AX4 (Figure 5).

[0019] The first hole 111 of link plate 110(D) is fitted to a fixing pin 157 embedded in the fixing plate 154 at a position spaced apart from the pivot pin 155, and is rotatably connected to the fixing pin 157. The second hole 112 of link plate 110(D) and the first hole 111 of link plate 110(E) are fitted to pin 123 and are rotatably connected relative to each other. The rotation axes of fixing pin 157 and pin 123 are parallel to the rotation axes of pins 121 and 122. The rotation axis of pin 123 is designated as the second base axis AX2 (Figure 5).

[0020] Furthermore, the third hole 113 of link plate 110(B) and the third hole 113 of link plate 110(D) are fitted to the pin 124 and connected so as to be rotatable relative to each other. The third hole 113 of link plate 110(E) and the third hole 113 of link plate 110(C) are fitted to the pin 125 and connected so as to be rotatable relative to each other. Also, the pin 124 is fitted to the hole 156b of the drive member 156 (see Figure 3) and connected so as to be rotatable relative to each other. The rotation axis of the pin 124 is the third base axis AX3 (Figure 5), and the rotation axis of the pin 125 is the fifth base axis AX5 (Figure 5). The rotation axes of pins 124 and 125 are parallel to the rotation axes of pins 121, etc. Note that in the link plate 110 at the end of the row, one of the three holes does not need to be used for connection.

[0021] Figure 5 illustrates a linkage mechanism including the first to fifth axis lines AX1 to AX5. Here, link plate 110(A) is designated as the first link, link plate 110(B) as the second link, link plate 110(D) as the third link, and link plate 110(E) as the fourth link, with the relationship between the axis lines explained using the second link as the reference. In the plane perpendicular to the first axis line AX1 (the plane of paper in Figure 5), the third axis line AX3 is positioned in one of a pair of regions that enclose the first straight line L1 passing through the first axis line AX1 and the fourth axis line AX4, i.e., the region on the right in Figure 5. However, the third axis line AX3 may also be positioned in the region on the left.

[0022] In a plane perpendicular to the first axis line AX1, the second straight line L2 connecting the third axis line AX3 and the first axis line AX1, and the third straight line L3 connecting the third axis line AX3 and the fourth axis line AX4, have different lengths.

[0023] Depending on the difference between the length of the second straight line L2 and the length of the third straight line L3, the differential angle between the first link plate 110(A) and the second link plate 110(B), and the differential angle between the third link plate 110(D) and the fourth link plate 110(E) change with respect to the rotation angle of the first link plate 110(A) relative to the third link plate 110(D).

[0024] When the angle θ between the second line L2 and the third line L3 is less than 90 degrees, the link mechanism becomes more flexible in the extension direction, opposite to the bending direction. On the other hand, when the angle θ between the second line L2 and the third line L3 is greater than 90 degrees, the link mechanism becomes more stable in the bending direction. Furthermore, when the angle θ between the second line L2 and the third line L3 is greater than 90 degrees, the prosthetic limb can be made thinner.

[0025] The third axis line AX3 is located on the fixed side (fixing plate 154 side) of the link mechanism 100 relative to the second axis line AX2, and on the tip side (opposite side from the fixing plate 154) of the link mechanism 100 relative to the first axis line AX1.

[0026] The relationships between the base axes described above are defined based on the second link. In contrast, if, for example, the link plate 110(C), which is the fifth link connected to the second and fourth links, is used as the reference, then the fourth base axis AX4 in Figure 5 constitutes the first base axis, the fifth base axis AX5 constitutes the third base axis, and the center line of the second hole 112 of the link plate 110(E) constitutes the second base axis. The same applies when links are connected to the end of the link plate 110(C).

[0027] Power is supplied from a power source (not shown) to drive the motor 152, and the driving force causes the pivot member 153 to pivot via the reduction mechanism. When the drive member 156 is displaced in the direction of arrow A in Figure 1, the pin 124 is displaced in the same direction, and the third hole 113 of the link plate 110 (D) is also displaced in the same direction.

[0028] Since the first hole 111 of the link plate 110(D) and the fixing pin 157 of the fixing plate 154 are rotatably fitted together, a moment is generated in the link plate 110(D) in a clockwise direction in Figure 1 with respect to the fixing pin 157, depending on the displacement of the third hole 113 of the link plate 110(D), and the link plate 110(D) rotates in the same direction.

[0029] Referring to Figure 5, when link plate 110(D) rotates clockwise, the third hole 113 of link plate 110(D) and the third hole 113 of link plate 110(B) are also displaced in the same direction. However, since the first hole 111 of link plate (A) and the second hole 112 of link plate (B) are rotatably connected, a moment is generated in link plate 110(A) clockwise in Figure 5 with respect to the second hole 112, and link plate 110(A) rotates in the same direction.

[0030] As described above, the third hole 113 of link plate 110(D) and the third hole 113 of link plate 110(B) are rotatably connected to link plate 110(D). Therefore, as link plate 110(A) rotates clockwise in Figure 1, the second hole 112 of link plate (B) is displaced clockwise around the third hole 113 in Figure 5. As a result, a moment is generated in link plate (B) clockwise in Figure 5, and link plate 110(B) rotates in the same direction.

[0031] The relationship between link plates 110(A), 110(B), and 110(D) also applies to the relationship between link plates 110(B), 110(C), and 110(E). Therefore, when link plate 110(B) rotates clockwise in Figure 1, a moment is generated in link plates 110(E) and 110(C) in the same clockwise direction in Figure 1, causing these link plates to rotate in the same direction.

[0032] This operation allows the fingertip member 160 attached to the link plate 110(C) to be displaced in a direction closer to the actuator 150, thereby enabling the bending motion of the prosthetic finger FG (see Figures 1-4). The actuator 150 only needs to pivot one link plate 110 relative to the other link plates 110.

[0033] In contrast, when the motor 152 is reversed, its driving force is transmitted to the pivot member 153 via the reduction mechanism, and the drive member 156 moves in the direction of arrow B in Figure 4. As a result, a force in the opposite direction is transmitted to the link plate 110(D), and each link plate is displaced so that the prosthetic finger FG extends, as shown in Figures 4-1.

[0034] In the above embodiment, the drive member 156 rotates the link plate 110(D) clockwise or counterclockwise, but the bending motion of the prosthetic finger FG can be similarly achieved by rotating any other link plate. Alternatively, for example, a coil spring can be provided at the base of the link plate 110(A) to bias the link plate 110(A) counterclockwise, and a wire can be provided instead of the drive member 156. In this case, the actuator 150 pulls the link plate 110(D) via the wire and rotates it clockwise, causing the prosthetic finger FG to bend. When the wire is released, the elastic force of the coil spring causes the link plate 110(A) to rotate counterclockwise, allowing the prosthetic finger FG to extend. The number of link plates is not limited to five, and they can be connected in two rows in a similar manner.

[0035] According to this embodiment, since the prosthetic finger FG can be constructed using a link mechanism 100 with link plates 110 of a common shape, a simple and low-cost prosthetic hand can be realized.

[0036] (Second Embodiment) Figure 6 is a perspective view from the back of the hand of the wearer with the prosthetic fingers FG1 and FG2, which include the link mechanism 200 according to the second embodiment, attached to the wearer's hand, and Figure 7 is a view from the palm side. Figures 8 to 10 are perspective views showing the flexion and extension movements of the prosthetic finger FG1. Note that the prosthetic fingers FG1 and FG2 constitute a part of the prosthetic hand.

[0037] This embodiment does not have an actuator, and uses the first joints of the remaining middle and little fingers to perform flexion and extension movements of the prosthetic fingers FG1 and FG2. The following description will focus on the prosthetic finger FG1 corresponding to the little finger, but the same applies to the prosthetic finger FG2 corresponding to the middle finger.

[0038] The link mechanism 200 has a plurality (five in this case) of link plates 210 having a common shape and thickness. As shown in Figures 8 to 10, the link plates 210 are trapezoidal in shape and have a first hole 211 and a second hole 212 at both ends in the longitudinal direction, and a third hole 213 and a fourth hole 214 formed so as to have an axis shifted relative to the plane containing the axis (rotation axis) of the first hole 211 and the second hole 212. The fitting pins that enable relative rotation in each hole are not shown in the figure. The rotation axes of each hole are parallel.

[0039] The link plates 210 are arranged in two parallel rows in series. In the figure, the link plates 210 in the first row (first joint) have a second hole 212 at the end on the base 251 side and are designated 210(A), 210(B), and 210(C) from the side closest to the back of the hand for identification purposes. In contrast, the link plates 210 in the second row (second joint), which are closer to the ring finger than the first row, have a first hole 211 at the end on the base 251 side and are designated 210(D) and 210(E) from the side closest to the back of the hand for identification purposes. Note that since link plate 210(C) also serves as a fingertip member, two of them are used, sandwiching link plate 210(B) from both sides. Link plate 210(A) constitutes the first link, link plate 210(B) constitutes the second link, link plate 210(D) constitutes the third link, link plate 210(E) constitutes the fourth link, and link plate 210(C) constitutes the fifth link.

[0040] A base 251 is attached to the hand HD, and a fixing plate 252 is attached to the base 251. The base 251 and the fixing plate 252 constitute the base end. A cylindrical member (fixing part) 253 is fitted to the first joint of the wearer's remaining little finger, and by swinging the first joint, the cylindrical member 253 can also swing relative to the base 251.

[0041] The fourth hole 214 of link plate 210(A) is rotatably mounted to a pin on the fixing plate 252. The first hole 211 of link plate 210(A) and the second hole 212 of link plate 210(B) are fitted to the same pin and connected so as to be rotatable relative to each other. Also, the first hole 211 of link plate 210(B) and the second hole 212 of link plate 210(C) are fitted to the same pin and connected so as to be rotatable relative to each other.

[0042] Although not shown in the diagram, the first hole 211 of link plate 210(D) is rotatably connected to a pin formed on the outer circumference of the fixing plate 252. The second hole 212 of link plate 210(D) and the first hole 211 of link plate 210(E) are fitted to the same pin and connected so as to be rotatable relative to each other.

[0043] Furthermore, the third hole 213 of the link plate 210(B) and the third hole 213 of the link plate 210(D) are fitted to the same pin and connected so as to be relatively rotatable. Further, the third hole 213 of the link plate 210(C) and the third hole 213 of the link plate 210(E) are fitted to the same pin and connected so as to be relatively rotatable. As described above, the connection between the link plates via the first hole 211, the second hole 212, and the third hole 213 is the same as that in the first embodiment.

[0044] Taking the center line of the first hole 211 of the link plate 210(A) as the first axis line, the center line of the first hole 211 of the link plate 210(D) as the second axis line, the center line of the third hole 213 of the link plate 210(B) as the third axis line, the center line of the first hole 211 of the link plate 210(B) as the fourth axis line, and the center line of the third hole 213 of the link plate 210(E) as the fifth axis line.

[0045] In addition, a stopper pin or the like can be fitted into the fourth hole 214 of the link plate 210 with its tip protruding, so that when the link plates 210 rotate relative to each other by a predetermined rotation or more, the stopper pin abuts against another link plate 210, thereby restricting over-rotation.

[0046] When the wearer tilts the first joint of the remaining little finger, the cylindrical member 253 tilts, the first hole 211 of the link plate 210(D) is displaced to the left in FIG. 8, and the link plate 210(D) rotates counterclockwise in FIG. 8.

[0047] When the link plate 210(D) rotates counterclockwise in FIG. 8, a counterclockwise moment occurs in the link plate 210(A) and the link plate 210(B) in the same manner as in the first embodiment. Further, in conjunction with this, a counterclockwise moment also occurs in the link plate 210(E) and the link plate 210(C) in FIG. 8. Thereby, the bending operation of the artificial finger FG1 can be performed (see FIGS. 8 to 10).

[0048] On the other hand, when the wearer raises the first joint of the remaining little finger, the link plate 210(D) rotates clockwise in FIG. 10 together with the cylindrical member 253, thereby generating a clockwise moment in the link plate 210(A) and the link plate 210(B) in FIG. 8. Further, in conjunction with this, a clockwise moment also occurs in the link plate 210(E) and the link plate 210(C) in FIG. 8. Thereby, the operation of extending the prosthetic finger FG1 can be performed.

[0049] According to the present embodiment, since the prosthetic fingers FG1 and FG2 can be bent and extended without using an actuator, miniaturization, weight reduction, and cost reduction of the prosthetic hand can be realized.

[0050] (Modification) FIG. 11 is a perspective view showing a link mechanism 200A according to a modification of the present embodiment. The link mechanism 200A is an arrangement in which the link mechanisms 200 are arranged in parallel. That is, the link mechanism 200A includes a first row C1 (link plate 210(A), link plate 210(B), link plate 210(C)), a second row C2 (link plate 210(D), link plate 210(E)), a third row C3 (link plate 210(D), link plate 210(E)), and a fourth row C4 (link plate 210(A), link plate 210(B), link plate 210(C)) arranged from the outside toward the ring finger side. The connection modes of the link plates 210(A), 210(B), and 210(C) in the first row C1 and the link plates 210(D) and 210(E) in the second row are the same as those in the second embodiment. Also, the connection modes of the link plates 210(A), 210(B), and 210(C) in the fourth row C4 and the link plates 210(D) and 210(E) in the third row are the same as those in the second embodiment. In this example, two rows of first joint portions and two rows of second joint portions are arranged in parallel.

[0051] Although not shown, the link plate 210(D) in the second row and the link plate 210(D) in the third row are connected via a cylindrical member fitted to the first joint of the remaining little finger, for example. However, the link plate 210(D) in the second row and the link plate 210(D) in the third row may be directly connected.

[0052] When the modified link mechanism 200A is applied to a prosthetic finger, the wearer can cause the link mechanism 200A to perform flexion and extension movements that mimic those of a prosthetic finger by tilting a cylindrical member fitted to the first joint of the little finger.

[0053] (Third Embodiment) Figure 12 is a perspective view of the link mechanism 300 according to the third embodiment. The link mechanism 300 can be used as a prosthetic finger of a prosthetic hand, similar to the embodiments described above.

[0054] The link mechanism 300 includes a first connecting plate 301, a second connecting plate 302 pivotally connected to the first connecting plate 301 around a first pivot axis O1, a third connecting plate 303 pivotally connected to the first connecting plate 301 around a second pivot axis O2, a fourth connecting plate 304 pivotally connected to the second connecting plate 302 around a third pivot axis O3, a fifth connecting plate 305 pivotally connected to the fourth connecting plate 304 around a fourth pivot axis O4, and a sixth connecting plate 306 pivotally connected to the fifth connecting plate 305 around a fifth pivot axis O5. The sixth connecting plate 306 is pivotally connected to the third connecting plate 303 around a sixth pivot axis O6, and the third connecting plate 303 and the fourth connecting plate 304 are pivotally connected around a seventh pivot axis O7. It is preferable that the first connecting plate 301 to the sixth connecting plate 306 have a common plate thickness. The first pivot axis O1 to the seventh pivot axis O7 are parallel to each other.

[0055] The first connecting plate 301 constitutes the base end, the second connecting plate 302 constitutes the first link, the fourth connecting plate 304 constitutes the second link, the third connecting plate 303 constitutes the third link, the sixth connecting plate 306 constitutes the fourth link, and the fifth connecting plate 305 constitutes the fifth link.

[0056] The third pivot axis O3 is designated as the first base axis, the sixth pivot axis O6 as the second base axis, the seventh pivot axis O7 as the third base axis, and the fourth pivot axis O4 as the fifth base axis.

[0057] When the first connecting plate 301 is, for example, the base end fixed to the base of a prosthetic hand, rotating the third connecting plate 303 counterclockwise in Figure 12 generates counterclockwise moments in the second connecting plate 302 and the fourth connecting plate 304 relative to the first connecting plate 301, and further counterclockwise moments are generated in the sixth connecting plate 306 and the fifth connecting plate 305, similar to the embodiment described above. This allows the link mechanism 300 to perform movements that mimic the bending motion of a prosthetic finger. The same operation occurs when any plate material other than the third connecting plate 303 is rotated counterclockwise relative to the first connecting plate 301.

[0058] In contrast, when the third connecting plate 303 is rotated clockwise in Figure 12, a clockwise moment is generated in the second connecting plate 302 and the fourth connecting plate 304 relative to the first connecting plate 301, and further, a clockwise moment is generated in the sixth connecting plate 306 and the fifth connecting plate 305. This allows the link mechanism 300 to perform a movement that mimics the motion of extending a prosthetic finger.

[0059] (Fourth Embodiment) Figure 13 is a perspective view of the link mechanism 400 according to the fourth embodiment. The link mechanism 400 can be used as a prosthetic finger of a prosthetic hand, similar to the embodiments described above.

[0060] The link mechanism 400 includes a first connecting plate 401, a second connecting plate 402 pivotally connected to the first connecting plate 401 around a first pivot axis O1, a third connecting plate 403 pivotally connected to the first connecting plate 401 around a second pivot axis O2, a fourth connecting plate 404 pivotally connected to the second connecting plate 402 around a third pivot axis O3, a fifth connecting plate 405 pivotally connected to the fourth connecting plate 404 and the third connecting plate 403 around a fourth pivot axis O4, a sixth connecting plate 406 pivotally connected to the fifth connecting plate 405 around a fifth pivot axis O5, and a seventh connecting plate 407 pivotally connected to the sixth connecting plate 406 around a seventh pivot axis O7. The seventh connecting plate 407 is pivotably connected to the third connecting plate 403 around the sixth pivot axis O6. Preferably, the first to seventh connecting plates 401 to 407 have a common plate thickness. The first to seventh pivot axes O1 to O7 are parallel to each other.

[0061] The first connecting plate 401 constitutes the base end, the second connecting plate 402 constitutes the first link, the fourth connecting plate 404 constitutes the second link, the third connecting plate 403 constitutes the third link, the sixth connecting plate 406 constitutes the fourth link, and the fifth connecting plate 405 and the sixth connecting plate 406 constitute the fifth link.

[0062] The third pivot axis O3 is designated as the first base axis, the sixth pivot axis O6 as the second base axis, the fourth pivot axis O4 as the third and fourth base axes, and the centerline of the fifth pivot axis O5 as the fifth base axis.

[0063] When the first connecting plate 401 is, for example, a proximal end fixed to the base of a prosthetic hand, rotating the third connecting plate 403 counterclockwise in Figure 13 generates counterclockwise moments in the second connecting plate 402, fourth connecting plate 404, sixth connecting plate 406, fifth connecting plate 405, and seventh connecting plate 407 relative to the first connecting plate 401, similar to the embodiment described above. This allows the link mechanism 400 to perform movements that mimic the bending motion of a prosthetic finger. The same operation occurs when any of the plate materials other than the third connecting plate 403 are rotated counterclockwise relative to the first connecting plate 401.

[0064] In contrast, when the third member 403 is rotated clockwise in Figure 13, clockwise moments are generated in the second connecting plate 402, the fourth connecting plate 404, the sixth connecting plate 406, the fifth connecting plate 405, and the seventh connecting plate 407 relative to the first connecting plate 401. This allows the link mechanism 400 to perform a movement that mimics the motion of extending a prosthetic finger.

[0065] (Fifth Embodiment) Figure 14 is a side view of the link mechanism 500 according to the fifth embodiment. Figure 15 is a perspective view showing a part of the link mechanism according to the fifth embodiment. Figures 16 and 17 are diagrams illustrating examples of specification changes in the fifth embodiment. The link mechanism 500 according to the fifth embodiment can also be incorporated into a prosthetic hand in the same way as the embodiments described above.

[0066] The link mechanism 500 here consists of four link plates 510 having a common shape. Referring to Figure 15, a single link plate 510 is formed from a right-angled isosceles triangular plate material, but its shape is not limited to this. To distinguish between the front and back surfaces, the first surface of the link plate 510 (shown in white in Figure 15) is designated as 514, and the second surface opposite the first surface 514 (shown in gray in Figure 15) is designated as 515. Here, the first link plate is designated as 510(A), the second link plate as 510(B), the third link plate as 510(D), and the fourth link plate as 510(E). In Figure 14, the first link plate 510(A) and the second link plate 510(B) are shown by solid lines, and the third link plate 510(D) and the fourth link plate 510(E) are shown by dotted lines. Figures 16(a) and 17(a) illustrate the first link plate 510(A), and Figures 16(b) and 17(b) illustrate the third link plate 510(D). The first link plate 510(A) and the second link plate 510(B) constitute the first joint, and the third link plate 510(D) and the fourth link plate 510(E) constitute the second joint.

[0067] Each link plate 510 has a circular first hole 511, a second hole 512, and a third hole 513. The third hole 513 is located near a right-angle corner, while the first hole 511 and the second hole 512 are located near the other corners. The distance between the centers of the third hole 513 and the first hole 511 is different from the distance between the centers of the third hole 513 and the second hole 512.

[0068] Referring to Figures 14 and 15, the third hole 513 of the first link plate 510(A) and the third hole 513 of the third link plate 510(D) are aligned, and the first link plate 510(A) and the third link plate 510(D) are connected so as to be rotatable relative to each other via a cylindrical first pin 521 fitted into the two third holes 513. At this time, the first surface 514 of the first link plate 510(A) and the first surface 514 of the third link plate 510(D) are placed facing each other. As a result, the second hole 512 of the first link plate 510(A) is brought close to the first hole 511 of the third link plate 510(D).

[0069] Similarly, the third hole 513 of the second link plate 510(B) and the third hole 513 of the fourth link plate 510(E) are connected so as to be rotatable relative to each other via a cylindrical second pin 522 fitted into the two third holes 513. At this time, the first surface 514 of the second link plate 510(B) and the first surface 514 of the fourth link plate 510(E) are placed facing each other. As a result, the second hole 512 of the second link plate 510(B) is brought close to the first hole 511 of the fourth link plate 510(E).

[0070] Furthermore, the second hole 512 of the third link plate 510(D) and the second hole 512 of the second link plate 510(B) are connected so as to be rotatable relative to each other via a third pin 523 that is fitted into the second hole 512.

[0071] Here, a link mechanism 500 is shown as an example, in which the first link plate 510(A) and the second link plate 510(B), and the third link plate 510(D) and the fourth link plate 510(E) are arranged in two rows. However, as described above, it is also possible to configure a link mechanism that extends long in the connection direction by connecting the parallel link plates with pins through the third hole, and connecting the series link plates with pins through the first and second holes.

[0072] An example of the operation of the link mechanism 500 according to the fifth embodiment will be described with reference to Figures 16 and 17. Here, an example is shown in which the first link plate 510(A) is fixed and the third link plate 510(D) is rotationally driven relative to the first link plate 510(A) manually or by an actuator.

[0073] We will compare specifications in which the distance D1 between the centers of the third hole 513 and the first hole 511 of the link plate, and the distance D2 between the centers of the third hole 513 and the second hole 512 are changed.

[0074] Figure 16(a) is a view of the first link plate 510(A) in the first specification from the first surface 514 side, and Figure 16(b) is a view of the third link plate 510(D) from the second surface 515 side. In this specification, the distance D1 between the centers of the third hole 513 and the first hole 511 of the link plate and the distance D2 between the centers of the third hole 513 and the second hole 512 are relatively different. In other words, the length of the first straight line connecting the centers of the third hole 513 and the first hole 511 and the length of the second straight line connecting the centers of the third hole 513 and the second hole 512 are relatively different.

[0075] In the state shown in Figure 16(c), when the rotation angle of the third link plate 510(D) relative to the first link plate 510(A) is β1, the differential angle of the second link plate 510(B) [and the fourth link plate 510(E) relative to the third link plate 510(D)] is γ1. From this state, when the third link plate 510(D) is rotated counterclockwise relative to the first link plate 510(A), the second link plate 510(B) and the fourth link plate 510(E) also rotate counterclockwise accordingly. As shown in Figure 16(d), when the rotation angle becomes β2 (approximately 0 here), the differential angle becomes γ2. Here, since (γ2 - γ1) > (β1 - β2), it can be seen that this link mechanism is a speed-increasing mechanism that increases the differential angle with respect to the rotation angle. The speed increase ratio R1 of the link mechanism in Figure 16 can be expressed as (γ2 - γ1) / (β1 - β2).

[0076] Figure 17(a) is a view of the first link plate 510(A) in the second specification from the first surface 514 side, and Figure 17(b) is a view of the third link plate 510(D) from the second surface 515 side. In this specification, the distance D3 between the centers of the third hole 513 and the first hole 511 of the link plate and the distance D4 between the centers of the third hole 513 and the second hole 512 are relatively close. In other words, the length of the first straight line connecting the centers of the third hole 513 and the first hole 511 and the length of the second straight line connecting the centers of the third hole 513 and the second hole 512 are relatively close.

[0077] In the state shown in Figure 17(c), when the rotation angle of the third link plate 510(D) relative to the first link plate 510(A) is β3, the differential angle of the second link plate 510(B) [and the fourth link plate 510(E) relative to the third link plate 510(D)] is γ3. From this state, when the third link plate 510(D) is rotated counterclockwise relative to the first link plate 510(A), the second link plate 510(B) and the fourth link plate 510(E) also rotate counterclockwise accordingly. As shown in Figure 17(d), when the rotation angle becomes β4 (approximately 0 here), the differential angle becomes γ4. Here, since (γ4 - γ3) > (β3 - β4), it can be seen that this link mechanism is also a speed-increasing mechanism that increases the differential angle with respect to the rotation angle. The speed increase ratio R2 of the link mechanism in Figure 17 can be expressed as (γ4 - γ3) / (β3 - β4).

[0078] Comparing Figures 16 and 17, it can be seen that the relationship of the speed increase ratio is R2 > R1. On the other hand, the difference in the distance between the centers is |D1-D2| > |D3-D4|, which means that the difference between the distance between the centers of the third hole 513 and the first hole 511 of the link plate and the difference between the distance between the centers of the third hole 513 and the second hole 512 is inversely proportional to the speed increase ratio. In other words, by setting the difference between the distance between the centers of the third hole 513 and the first hole 511 of the link plate and the difference between the distance between the centers of the third hole 513 and the second hole 512, a desired speed increase ratio can be obtained.

[0079] This specification includes the following disclosures of the invention: (First aspect) A link mechanism comprising: a first joint portion including a first link and a second link rotatably connected to the first link about a first base axis; and a second joint portion parallel to the first joint portion, including a third link and a fourth link rotatably connected to the third link about a second base axis different from the first base axis, wherein the third link is rotatably connected to the second link about a third base axis different from the first and second base axes.

[0080] (Second embodiment) A link mechanism according to the first embodiment, characterized in that it has a fifth link which is rotatably connected to the second link around a fourth axis which is different from the first to third axis, and which is rotatably connected to the fourth link around a fifth axis which is different from the first to fourth axis, and the first joint includes the first link, the second link, and the fifth link which are connected in series.

[0081] (Third embodiment) The link mechanism of the second embodiment, characterized in that, in a plane perpendicular to the first base axis, the third base axis is located in one of a pair of regions that enclose a first straight line passing through the first base axis and the fourth base axis.

[0082] (Fourth embodiment) A link mechanism according to the second or third embodiment, characterized in that, in a plane perpendicular to the first base axis, the second straight line connecting the third base axis and the first base axis and the third straight line connecting the third base axis and the fourth base axis are of different lengths.

[0083] (Fifth embodiment) A link mechanism of the fourth embodiment, characterized in that the differential angle of the fourth link with respect to the third link with respect to the rotation angle of the second link with respect to the first link changes according to the difference between the length of the second straight line and the length of the third straight line.

[0084] (Sixth aspect) A link mechanism according to any of the second to fifth aspects, characterized in that the angle between the second straight line and the third straight line is less than 90 degrees.

[0085] (Seventh embodiment) A link mechanism according to any of the second to sixth embodiments, characterized in that the third base axis is located on the fixed portion side of the link mechanism with respect to the second base axis and on the tip side of the link mechanism with respect to the first base axis.

[0086] (Eighth aspect) A link mechanism according to any of the second to seventh aspects, characterized in that the first to fifth base axes are parallel to each other.

[0087] (Ninth aspect) A link mechanism according to any of the second to eighth aspects, characterized in that the first to fourth links are formed from plate material of a common thickness.

[0088] (Tenth aspect) A link mechanism according to any of the second to ninth aspects, characterized in that the first to fourth links have a common shape with respect to each other.

[0089] (Eleventh aspect) A prosthetic hand characterized by having a link mechanism according to any of the first to tenth aspects.

[0090] (Twelfth embodiment) The prosthetic hand of the eleventh embodiment, characterized in that it has an actuator that pivots at least one of the first to fourth links relative to the other links.

[0091] (Third embodiment) A prosthetic hand according to the eleventh or twelfth embodiment, characterized in that it moves integrally with a part of the fingers of the wearer of the prosthetic hand and has a fixed part connected to at least one of the first to fourth links.

[0092] 100, 200, 300, 400, 500 Link mechanism 110, 210, 510 Link plate 111, 511 First hole 112, 512 Second hole 113, 513 Third hole 121, 122, 123, 124 Pin 157, 158 Fixing pin 150 Actuator 253 Cylindrical member 301-306, 401-406 Connecting plate β1, β2, β3, β4 Rotation angle γ1, γ2, γ3, γ4 Differential angle

Claims

1. A link mechanism comprising: a first joint portion including a first link and a second link rotatably connected to the first link around a first base axis; and a second joint portion parallel to the first joint portion, including a third link and a fourth link rotatably connected to the third link around a second base axis different from the first base axis, wherein the third link is rotatably connected to the second link around a third base axis different from the first and second base axes.

2. The link mechanism according to claim 1, wherein the second link is rotatably connected to the fourth link around a fourth axis different from the first to third axis lines, and the fourth link is rotatably connected to the fourth link around a fifth axis different from the first to fourth axis lines, and the first joint includes the first link, the second link, and the fifth link connected in series.

3. The link mechanism according to claim 2, characterized in that, in a plane perpendicular to the first base axis, the third base axis is positioned in one of a pair of regions that enclose a first straight line passing through the first base axis and the fourth base axis.

4. The link mechanism according to claim 2, characterized in that, in a plane perpendicular to the first base axis, the second straight line connecting the third base axis and the first base axis and the third straight line connecting the third base axis and the fourth base axis are of different lengths.

5. The link mechanism according to claim 4, characterized in that the differential angle of the fourth link with respect to the third link with respect to the rotation angle of the second link with respect to the first link changes according to the difference between the length of the second straight line and the length of the third straight line.

6. The link mechanism according to claim 4, characterized in that the angle between the second straight line and the third straight line is less than 90 degrees.

7. The link mechanism according to claim 2, characterized in that the third base axis is located on the fixed portion side of the link mechanism with respect to the second base axis and on the tip side of the link mechanism with respect to the first base axis.

8. The link mechanism according to claim 2, characterized in that the first to fifth base axes are parallel to each other.

9. The link mechanism according to claim 2, characterized in that the first to fifth links are formed from a plate material of a common thickness.

10. The link mechanism according to claim 2, characterized in that the first to fifth links have a common shape with respect to each other.

11. A prosthetic hand characterized by having a link mechanism as described in any one of claims 1 to 5.

12. The prosthetic hand according to claim 11, further comprising an actuator that pivots at least one of the first to fourth links relative to the other links.

13. The prosthetic hand according to claim 11, characterized in that it moves integrally with a part of the fingers of the wearer of the prosthetic hand and has a fixed part connected to at least one of the first to fourth links.

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