US3927424A

US3927424A - Mechanical hand

Info

Publication number: US3927424A
Application number: US435214A
Authority: US
Inventors: Hideyo Itoh
Original assignee: Agency of Industrial Science and Technology
Current assignee: National Institute of Advanced Industrial Science and Technology AIST
Priority date: 1973-01-19
Filing date: 1974-01-21
Publication date: 1975-12-23
Anticipated expiration: 1992-12-23
Also published as: JPS4995357A; JPS5420749B2

Abstract

A mechanical hand comprises a palm element and at least two finger elements and incorporates a closed link mechanism. The two finger elements are connected at their basal ends, each with a joint, the first one to the palm element and the second one to the forward end of the first finger element, respectively. The closed link mechanism is constructed of the first finger element in combination with a projecting bar which stems at a certain angle from the basal end of the second finger element and constitutes a unitary part in conjunction with the second finger element. Driving this closed link mechanism by an actuator sets the finger elements to movement. When any portion of the finger elements comes into contact with an obstacle standing in its way, the closed link mechanism begins to change its form. In consequence of this change of form, the first finger element and/or the second finger element begins to turn round the joint as a pivot and continues, while adapting the form of the mechanical hand to the immediate environment, to converge in the direction of gradually conforming to the exterior contour of an object desired to be gripped and eventually gripping the object.

Description

[ Dec. 23, 1975 MECHANICAL HAND [75] Inventor: Hideyo Itoh, Tokyo, Japan [73] Assignee: Agency of Industrial Science &

Technology, Tokyo, Japan [22] Filed: Jan. 21, 1974 [21] Appl. No.: 435,214

[30] Foreign Application Priority Data Jan. 19, 1973 Japan 48-8431 [52] US. Cl. 3/12.6; 214/1 CM; 294/106; 3/12 [51] Int. Cl. A61F 1/06 [58] Field of Search 3/l2l2.8, 3/1.2, 1.1; 214/1 CM; 294/106 Primary ExaminerRonald L. Frinks Attorney, Agent, or Firm-Oblon, Fisher, Spivak, McClelland & Maier [57] ABSTRACT A mechanical hand comprises a palm element and at least two finger elements and incorporates a closed link mechanism. The two finger elements are connected at their basal ends, each with a joint, the first one to the palm element and the second one to the forward end of the first finger element, respectively. The closed link mechanism is constructed of the first finger element in combination with a projecting bar which stems at a certain angle from the basal end of the second finger element and constitutes a unitary part in conjunction with the second finger element. Driving this closed link mechanism by an actuator sets the finger elements to movement. When any portion of the finger elements comes into contact with an obstacle standing in its way, the closed link mechanism begins to change its form. In consequence of this change of form, the first finger element and/or the second finger element begins to turn round the joint as a pivot and continues, while adapting the form of the mechanical hand to the immediate environment, to converge in the direction of gradually conforming to the exterior contour of an object desired to be gripped and eventually gripping the object 6 Claims, 15 Drawing Figures US. Patent Dec. 23, 1975 Sheet 1 of 4 3,927,424

1 7MB 9 N' 5 U.S. Patent Dec. 23, 1975 Sheet 2 of4 3,927,424

Fig.2(D)

U.S. Patent Dec.23, 1975 Sheet3of4 3,927,424

Fi 3 Fig.4(A)

A /II US. Patent Dec. 23, 1975 Sheet 4 of4 3,927,424

Fig-5(A) 32 231) 2422 25 MECHANICAL HAND BACKGROUND OF THE INVENTION This invention relates to a mechanical hand. More particularly, the present invention relates to an adaptable mechanical hand which is capable of adapting its movement to the immediate environment within a prescribed range so as to provide stable gripping of a desired object.

Mechanical hands are generally used as means for loading and unloading in production lines and as prosthetic hands. Particularly, mechanical hands which are easy of control and yet applicable to numerous purposes involving varying working conditions are in demand.

The mechanical hands heretofore known are such that some require highly complicated mechanisms in order for them to be adapted to varying working conditions of numerous purposes and others involve complicated controls notwithstanding the simplicity of their own mechanisms. For example, the Belgrade hand, which has long been known, can have its finger elements easily moved by an actuator. When any of the finger elements of the Belgrade hand collides with an obstacle en route to the object to be gripped, however, the hand can no longer continue its movement, so that the hand cannot grip the desired object unless the support of the hand is moved to a new position.

An object of this invention is to provide a mechanical hand which possesses a mechanism capable of adapting the movement of the mechanical hand itself to the immediate environment without requiring any complicated control system and which, therefore, permits the movement of the mechanical hand to continue until the desired object is gripped thereby.

Another object of this invention is to provide a mechanical hand which gradually changes its own form so as to conform to the contour of the object to be gripped and eventually grip the object as desired.

SUMMARY OF THE INVENTION To accomplish the objects described above, the mechanical hand according to this invention comprises a palm element and at least two finger elements connected at their basal ends each with a joint, the first one to the palm element and the second one to the forward end of the first finger element, respectively, and incorporates a closed link mechanism composed of the whole or a part of the first finger element in combination with a projecting bar stemming at a certain angle from the basal end of the second finger element and constituting a unitary part in conjunction with the second finger element, and utilizes an actuator which serves the purpose of driving the closed link mechanism. The mechanical hand according to this invention has a construction as described above. When the mechanical hand is set to movement and any portion of the finger elements thereof comes into contact with an obstacle standing in its way, the closed link mechanism begins to change its form. In consequence of the change in the shape of the link, the first finger element and/or the second finger element turns round the joint as a pivot and continues, while adapting the form of the mechanical hand to the immediate environment, to converge in a direction for eventually gripping the object to be gripped. When the mechanical hand comes into contact with the object, the closed link mechanism functions so as to cause the first and second finger elements to assume an angular relationship conforming to the exterior contour of the object, thus providing stable gripping of the object.

As used in the specification and the claims hereof, the term basal end of a finger means the extremity of the finger element closer to the palm element and the term forward end of a finger means the extremity of the finger element farther from the palm element.

Other objects and other characteristics of the present invention will become apparent from the description which is made in further detail herein below with reference to the accompanying drawings.

BRIEF EXPLANATION OF THE DRAWING FIG. 1(A) is a schematic drawing of the construction of the known Belgrade hand.

FIG. 1(B) and FIG. 1(C) are explanatory diagrams illustrating the modes of movement of the Belgrade hand of FIG. 1(A).

FIG. 2(A) is a schematic drawing illustrating one preferred embodiment of the mechanical hand according to the present invention.

FIG. 2(B) through (D) are explanatory diagrams illustrating the modes of movement of the mechanical hand of FIG. 2(A).

FIG. 3 is a schematic drawing illustrating another embodiment of the mechanical hand according to this invention.

FIG. 4(A) through (C) are explanatory diagrams illustrating the modes of movement of the mechanical hand as operated to grip an object laid in a special environment such as, for example, a groove.

FIG. 5(A) is a schematic drawing illustrating still another embodiment of the mechanical hand according to the present invention.

FIG. 5(B) through (D) are explanatory diagrams illustrating the modes of movement of the mechanical hand of FIG. 5(A).

DETAILED DESCRIPTION OF THE INVENTION FIG. 1(A) represents a Belgrade hand which has heretofore been known. To a palm element 1, the first, second and

third finger elements

2, 3 and 4 are connected serially each by means of joints. Further, a projecting bar 5 stemming at a certain angle from the basal end of the second finger element 3 has its forward end connected to the forward end of a rod 6 which in turn is connected at its basal end to a palm element 1. Another projecting bar 7 stemming at a certain angle from the basal end of the third finger element 4 is connected via a rod 8 with a joint to the projecting bar 9 which stems from the first finger element 2. The finger elements of this mechanical hand are put to movement when a projecting bar 10 fastened to the basal end of the first finger element 2 is driven by means of an actuator (not illustrated). Since the finger elements are connected each by means of a joint, their movements are obtained only in a prescribed space. When an obstacle occurs in any of such prescribed spaces, therefore, the movements of the finger elements can no longer be obtained beyond that obstacle. Take, for example, a case in which this mechanical hand is operated to grip an object 11 laid on a table. If no obstacle occurs in the spaces for the movements of the finger elements, then the finger elements turn round their respective joints until they take a stable grip of the object as illustrated in FIG. 1(B). If any obstacle occurs in such spaces so that the mechanical hand comes into contact with the obstacle prior to reaching the object to be gripped (FIG. 1(C)), however, the movements of the finger elements are stopped and consequently prevented from reaching the point of taking a stable grip of the object. In order for the mechanical hand to grip the object despite the presence of such obstacle, therefore, it has heretofore been inevitably necessary for the operator to observe the operation of the mechanical hand and, whenever such collision of the forward end of the third finger element against the table top is detected, change the position of the palm element by suitably moving the base supporting the hand to a new position at which such collision may be avoided.

The present invention concerns a mechanical hand possessed of a mechanism absolutely free from such complicated control of movement. The preferred embodiment of the invention given in FIG. 2 represents a mechanical hand which possesses two joints. The first finger element 13 is connected at its basal end with a first free rotation joint 15 to a first stationary surface, on palm element, 12 and the second finger element 14 is connected at its basal end with a second free rotation joint 16 to the forward end of said first finger element 13. A projecting bar 17 stems at a certain angle from the basal end of the second finger element 14 and constitutes a unitary part in conjunction with the second finger element 14. The forward end of the projecting bar 17 is connected with a third free rotation joint 23 to the forward end of a first rod 18, whose basal end is connected with a fourth free rotional joint 24 to the forward end of a projecting rod 19 connected at the basal end thereof with a fifth joint 21 to the first finger element. A part of the first finger element 13 goes to make up a closed link mechanism in conjunction with the projecting bar 17 and the

rods

18 and 19. Alternately, the closed link mechanism 20 may be formed by the whole of the first finger element 13 taken in conjunction with the projecting bar 17 and the

rods

18 and 19 as illustrated in FIG. 3. One end of a second rod 22 is connected to the joint 24 and the other end of said rod 22 is connected through a sixth joint 38 to one end of a third rod 25 the other end of which is connected to a seventh joint 39 of a second stationary surface, or palm element, 26. The rod 25 is connected via a rod 28 to the piston rod of an actuator 27. In this preferred embodiment, two mechanical hands of the construction described above are disposed symmetrically.

In order that the mechanical hands of the present invention having the aforementioned construction may grip an object 11 as desired, the rods 28 of the actuator 27 are to be driven downwardly as illustrated in FIG. 2(B). Consequently, the rods 25 are diverged and, as the joints 15 are fastened more loosely than any other joint, the mechanical hands are allowed to turn round the joints 15 as pivots, as illustrated in FIG. 2(B), with the result that the forward ends of the second finger elements 14 collide into an obstacle which, in the illustrated case, is a table top. As the rods 28 of the actuator 27 are further driven downwardly, the movements of the second finger elements 14 are restricted and the closed link mechanisms 20 begin to change their form, as shown in FIG. 2(C), causing the forward ends of the second finger elements 14 to move on the table top toward each other and eventually grip the object 1 1, as if embracing it (FIG. 2(D)).

The mechanical hands may be so constructed that they will be first bent round the joints 16 in the initial stage of operation. At which pair of joints the mechanical hands are required to be bent first is a question to be decided at the time of the overall design in accordance with the object to be gripped and the environment in which the gripping is to be made. In any event, the mechanical hands are so designed that the finger elements will eventually assume an angular relationship most suitable for gripping the object, as illustrated in FIG. 2(D). The closed link mechanisms 20 serve to provide necessary allowance for the movements of the first and

second finger elements

13 and 14. The motion provided by the actuator 27 is conveyed, in adequate compliance with the immediate environment of the operation, to the first or second finger element by the medium of the closed link mechanisms which function as one kind of idle element. Because of the idling function of the link mechanism, the finger elements of the mechanical hands produce movements well adapted to the environment, including the object to be gripped, without requiring use of any special control system.

In this particular example, a piston is employed as the means for driving the mechanical hands. Altemately, the combination of a motor and a cam and other suitable known driving means may be effectively employed as well.

FIG. 4 illustrates the mode of movement of the mechanical hand as operated to take a grip of an object which is laid in a special environment, such as, for example, a groove 34. As the actuator produces a driving motion, the mechanical hands turn round the joints l5 and cause the forward ends of the second finger elements 14 to come into contact with the table top and then move on the table top toward each other (FIG. 4(B)). As the forward ends of the second finger elements 14 reach the edges of the groove 34 and then fall into the groove, the closed link mechanism 20 immediately begin to change their form so as to permit the forward ends of the finger elements to descend slowly toward the bottom of the groove. As the forward ends of the second finger elements reach the bottom of the groove, they again begin to move toward each other to continue their movements for gripping the object. Thus, the mechanical hands provide the stablest gripping of the object in much the same way as they are operated to take a grip of an object laid on a flat surface.

The preferred embodiment illustrated in FIG. 5(A) represents a pair of mechanical hands each possessed of three joints. In each of the mechanical hands, a third finger element 29 is connected at its basal end with an eighth joint 30 to the forward end of the second finger element of the mechanical hand illustrated in FIG. 2. A second projecting bar 31 constituting a unitary part with the third finger element 29 stems at a certain angle from the basal end of the third finger element. The forward end of the projecting bar 31 is connected with a ninth joint 33 to the forward end of a fourth rod 32, whose basal end is connected with a tenth joint 37 to the first finger element.

When an actuator (not illustrated) is operated on the mechanical hands described above, the rods are diverged relative to the palm element 26 as illustrated in FIG. 5(B), causing the closed link mechanisms 20 to change their form. Consequently, the projecting bars 17 of the second finger elements 14 are turned round the joints 16, with the result that the second finger elements 14 are bent with reference to the first finger elements 13. In consequence of this bending, the closed link mechanisms 20 function to bend the third finger elements 29 with reference to the second finger elements 14. As the forward ends of the third finger elements collide with an obstacle, such as, for example, a table top, the forward ends of the third finger elements 29 are prevented from continuing their movement'in that direction, with the result that the revolution of the first finger elements 13 round their respective joints is stopped. The driving motion of the actuator isnow used in changing the form of the closed link mechanisms 20, so that the second finger elements 14, and consequently the third finger elements 29, are turned further. The forward ends of the third finger elements 29, therefore, move on the table top toward each other and continue their movements for gripping the object, as illustrated in FIG. (C). There are cases in which the first finger elements may be revolved in a reverse direction in consequence of the-movement of theforward ends of finger elements toward each other.

When the forward ends of the finger elements come into contact with the object, the individual finger elements are bent round their respective joints so as to take an embracing grip of the object, as illustrated in FIG. 5(D).

An observation of the movements of a human hand reveals that the fingers of the human hand in the process of taking a grip at an object move in three ways: In the first way, the first joints move mainly during the initial stage and the second and eighth joints move mainly during the subsequent stage. In the second way, the second and eighth joints move mainly during the initial stage and the first joints move mainly during the subsequent stage. In the third way, all the joints move in a fixed positional relationship. In any way, the movements of the second and eighth joints are in a practically proportional relationship, though they are adapted to the immediate environment in which the gripping operation is in process. That which specially matters in having the joints of fingers adapt to greatly varying working conditions is the question as to what relative movements the first and second joints make. In the aforementioned mechanical hands each possessed .of two joints or of three joints, therefore, it is extremely important that the first joint 15 and the second joint 16 should produce movements adapted to the environment. The adaptable gripping movements of the finger elements are not particularly affected even if the second joints 16 and the eighth joints 30 are caused by the closed link mechanisms to make a interrelated movement. One may rather conclude safely that the movements of the latter mechanical hands are similar to the gripping movements of a human hand.

If occasion demands, the second and third finger elements may be fastened immovably toeach other or they may be interlocked to each other so as to produce movements adapted to the environment similarly to the aforementioned relationship between the first and second finger elements.

The preferred embodiments so far described each represent a case in which two mechanical fingers of an identical construction are symmetrically disposed. Depending on the purpose of an individual application, however, two mechanical fingers differing in construction may be combined and used as one pair. Alternately, one mechanical finger and a mere rod may be combined so that desired gripping of an object will be obtained by the cooperation of the mechanical finger and the rod, with the rod serving the purpose of holding the gripped object in position in the subsequent process of lifting. .t

As is apparent from the foregoing description, the mechanical hands according to the present invention have closed link mechanisms which enable the finger elements to produce movements adapted in fixed spaces to the immediate environment without requiring use of any complicated control. Because of the adaptability of movement coupled with the extreme simplicity of construction, the mechanical hands of this invention can be used for a rich variety of purposes.

What is claimed is:

1. A mechanical hand comprising:

a first free rotation joint;

a second free rotation joint;

a third free rotation joint;

a fourth free rotation joint;

a fifth free-rotation joint;

a sixth free rotation joint;

a seventh free rotation joint;

a first rod;

a second rod;

a third rod;

a projecting rod;

a projecting bar;

a first finger element;

a second finger element;

a first stationary surface;

a second stationary surface;

said second finger element and said projecting bar being rigidly joined at a predetermined angle; said first joint joining said first finger element to said first stationary surface;

said second joint joining said first finger element to the junction of said second finger element and said projecting bar;

said third joint joining said first rod and said projecting bar;

said fourth joint joining said second rod, said first rod and said projecting rod;

said fifth joint joining said first finger element and said projecting rod;

said sixth joint joining said second rod to said third rod;

said seventh joint joining said third rod to said second stationary surface;

whereby an object may be gripped upon the application of pressure to said third rod.

2. A mechanical hand in accordance with claim 1 wherein two mechanical hands are symmetrically disposed and joined at said seventh joint.

3. A mechanical hand in accordance with claim 1, wherein said first and said fifth joints comprise a single joint joining said first finger element and said projecting rod and connecting the same to said first stationary surface.

4. A mechanical hand in accordance with claim 3 wherein two mechanical hands are symmetrically disposed and joined at said seventh joint. 5. A mechanical hand comprising: a first free rotation joint; a second free rotation joint; a third free rotation joint; a fourth free rotation joint; a fifth free rotation joint; a sixth free rotation joint;

a seventh free rotation joint;

an eighth free rotation joint;

21 ninth free rotation joint;

a tenth free rotation joint;

a first rod;

a second rod;

a third rod;

a fourth rod;

a projecting rod;

a first projecting bar;

a second projecting bar;

a first finger element;

a second finger element;

a third finger element;

a first stationary surface;

a second stationary surface;

said second finger element and said first projecting bar being rigidly joined at a predetermined angle;

said third finger element and said second projecting bar being rigidly joined at a predetermined angle;

said first joint joining said first finger element rotatively to said first stationary surface;

said second joint joining said first finger element and the junction of said first projecting bar and second finger element;

said third joint joining said first rod and said first projecting bar;

said fifth joint joining said projecting rod and said first finger element;

said sixth joint joining said second rod and said third rod;

said seventh joint joining said third rod and said second stationary surface;

said eighth joint joining said second finger element and the junction of said third finger element and said second projecting bar;

said ninth joint joining said fourth rod and said second projecting bar;

said tenth joint joining said fourth rod to said first finger element at a point intermediate the ends of said first finger element;

6. A mechanical hand in accordance with claim 5 wherein two mechanical hands are symmetrically disposed and joined at said seventh joint.

Claims

1. A mechanical hand comprising: a first free rotation joint; a second free rotation joint; a third free rotation joint; a fourth free rotation joint; a fifth free rotation joint; a sixth free rotation joint; a seventh free rotation joint; a first rod; a second rod; a third rod; a projecting rod; a projecting bar; a first finger element; a second finger element; a fiRst stationary surface; a second stationary surface; said second finger element and said projecting bar being rigidly joined at a predetermined angle; said first joint joining said first finger element to said first stationary surface; said second joint joining said first finger element to the junction of said second finger element and said projecting bar; said third joint joining said first rod and said projecting bar; said fourth joint joining said second rod, said first rod and said projecting rod; said fifth joint joining said first finger element and said projecting rod; said sixth joint joining said second rod to said third rod; said seventh joint joining said third rod to said second stationary surface; whereby an object may be gripped upon the application of pressure to said third rod.

4. A mechanical hand in accordance with claim 3 wherein two mechanical hands are symmetrically disposed and joined at said seventh joint.

5. A mechanical hand comprising: a first free rotation joint; a second free rotation joint; a third free rotation joint; a fourth free rotation joint; a fifth free rotation joint; a sixth free rotation joint; a seventh free rotation joint; an eighth free rotation joint; a ninth free rotation joint; a tenth free rotation joint; a first rod; a second rod; a third rod; a fourth rod; a projecting rod; a first projecting bar; a second projecting bar; a first finger element; a second finger element; a third finger element; a first stationary surface; a second stationary surface; said second finger element and said first projecting bar being rigidly joined at a predetermined angle; said third finger element and said second projecting bar being rigidly joined at a predetermined angle; said first joint joining said first finger element rotatively to said first stationary surface; said second joint joining said first finger element and the junction of said first projecting bar and second finger element; said third joint joining said first rod and said first projecting bar; said fourth joint joining said second rod, said first rod and said projecting rod; said fifth joint joining said projecting rod and said first finger element; said sixth joint joining said second rod and said third rod; said seventh joint joining said third rod and said second stationary surface; said eighth joint joining said second finger element and the junction of said third finger element and said second projecting bar; said ninth joint joining said fourth rod and said second projecting bar; said tenth joint joining said fourth rod to said first finger element at a point intermediate the ends of said first finger element; whereby an object may be gripped upon the application of pressure to said third rod.