Artificial hand for grasping an object

An artificial hand includes a finger group which is pivotally connected to a thumb. The finger group and thumb are resiliently biased toward one another. The finger group and thumb have hooked articulated distal ends. When the artificial hand and the object are brought together, the finger-group and the thumb part to allow the object to pass into a capture zone. The articulated distal ends bend inwardly to assist in the passage of the object. Once in the capture zone the finger group and thumb close about the object thereby holding it is place. The hooked distal ends also serve to retain the object within the capture zone. In another aspect of the invention the finger group includes two finger subgroups which are also resiliently biased together to hold objects.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains generally to the field of prosthetics, and more particularly, to a method and associated apparatus for using an artificial hand to hold objects.

2. Description of the Prior Art

Artificial hands are well know in the art, and are utilized as a substitute for a hand which has been lost through amputation or birth defect. Some artificial hands employ a push button(s) to open and close the hand, consequently requiring additional steps which interrupt the natural use pattern of handling an object. Other artificial hands are operated through a cable or motors which can be controlled by muscular contractions of other parts of the user's body.

SUMMARY OF THE INVENTION

The present invention is directed to a method and associated apparatus for using an artificial hand to grasp an object. The operative principle of this invention is that it provides a device (called Easy-Feed) to receive and securely grasp an object in a manner that is as natural as possible; namely, one simply pushes the object directly against the dorsal (outer) surface of the fingertips to cause the hand to open and receive the object. The invention employs finger groups which easily move apart as the object and fingers are brought together in a natural manner. Once the object resides in the capture zone, the finger groups resiliently close about the object to retain it in position. A useful feature of the invention is that the force required to insert an object is usually less than the force required to release the object. We use the terms “self-energizing” and “natural” because the user simply pushes the object directly through the fingers into the secure grasp of te hand. No extra cognitive or physiological burden is placed upon the user to manipulate a cable and harness, activate myoelectric signals, or actuate auxiliary buttons in order to operate the hand.

In accordance with a preferred embodiment of the invention, an artificial hand for grasping an object comprises a first finger group movably connected to a second finger group wherein the first and second finger groups are resiliently biased toward one another. The finger groups have mutually facing volar surfaces and opposite dorsal surfaces. The volar surfaces of the first and second finger groups define a capture zone within which objects are held. When an object is pushed against the dorsal surfaces at the finger group ends, the first and second finger groups, upon contacting the object, spread away from each other, thereby accepting the object and allowing the object to pass into the capture zone. Once the object resides in the capture zone, the first and second finger groups resiliently close around the object to retain the object in place within the capture zone.

According to the invention, the first finger group includes a plurality of fingers (two in a preferred embodiment), and the second finger group includes a thumb. The plurality of fingers and the thumb residing in opposing relationship wherein the volar surfaces of the plurality of fingers and the thumb are curved toward one another to form the capture zone. The plurality of fingers and the thumb cooperate to form an object handling mechanism wherein, when an object is pushed against the dorsal surfaces at the tips of the finger groups with a first force, the plurality of fingers and the thumb spread away from each other allowing the object to pass into the capture zone. After the object passes into the capture zone, the plurality of fingers and the thumb resiliently close around the object in a grasping action.

When the artificial hand and the object are pulled apart with a second force, the plurality of fingers and the thumb spread away from each other thereby releasing the object. Due to the construction of the present invention, the second force is usually greater than the first force.

According to the invention, the plurality of fingers and the thumb each have a distal end. At least some of the distal ends are hook-shaped and articulated. That is, the distal ends are hooked or curved inwardly toward the capture zone. The hooked shaped helps retain the object within the capture zone, and the articulated distal ends bend inwardly to accept the object. Mechanical stops prevent the articulated distal ends from bending outwardly beyond a maximum limit.

In one broad aspect the present invention may be considered to be an artificial hand for grasping an object comprising a base and first and second finger groups movably joined to the base. Each of the finger groups has volar and dorsal surfaces, and a distal end. The finger groups are resiliently biased toward each other and define a capture zone between the Volar surfaces thereof. The finger groups are movable relative to each other between open and closed positions. In the closed position the finger groups define a plane of object entry between the distal ends of the finger groups. This plane of object entry extends through the capture zone and intersects the base. When the object is pushed along the plane of object entry against the dorsal surfaces of the distal ends of the finger groups, the distal ends of the first and second finger groups then spread apart from each other, thereby accepting the object and allowing the object to pass between the volar surfaces of the first and second finger groups and enter the capture zone. When this occurs the first and second finger groups resiliently close around the object to retain it within the capture zone.

In another broad aspect the invention may be considered to be an artificial hand comprised of a base and a pair of opposing finger groups connected to the base. Both of the finger groups have dorsal and volar surfaces and distal ends. At least one of the finger groups is a movable finger group with an instantaneous axis of rotation relative to the base so that the finger groups form a capture zone therebetween and are movable relative to each other between open and closed positions. In the closed positions the finger groups define a plane of object entry extending between the distal ends of the finger groups, through the capture zone and intersecting the base. The instantaneous axis of rotation for the movable finger group lies on the opposite side of the plane of object entry from the distal end of the movable finger group, when the finger groups are in the closed position. As a result, when an object is pushed along the plane of object entry against the dorsal surfaces of the distal ends of the finger groups, the finger groups then spread apart from each other, thereby accepting the object and allowing the object to pass between the volar surfaces of the finger groups and enter the capture zone, whereupon the finger groups resiliently close around the object to retain it within the capture zone.

In accordance with another aspect of the invention the plurality of fingers are connected to the body at a first pivotal axis and the thumb is connected to the body at a second pivotal axis. The pivotal axes are arranged in a crossover configuration wherein the pivotal axes are positioned toward the opposite member. This design provides the easy opening feature of the present invention.

In accordance with another aspect of the invention, the first finger group includes a first finger subgroup and a second finger subgroup which are resiliently biased toward one another. A second object may be placed between the first finger subgroup and the second finger subgroup and retained in place. The closing action of the first and second finger subgroups operates substantially perpendicular to the closing action of the plurality of fingers and the thumb.

The invention may be described with greater clarity and particularity by reference to the accompanying drawings.

DESCRIPTION OF THE EMBODIMENT

Referring initially toFIGS. 1–3, there are illustrated top plan, side elevational, and perspective views, respectively, of an artificial hand for grasping objects in accordance with the present invention, generally designated as20. The artificial hand20includes a first finger group22movably connected to a second finger group24wherein the first finger group22and the second finger group24are resiliently biased toward one another as shown inFIG. 2.FIG. 4shows the first finger group22and the second finger group24pivoted to an open position. The first finger group22pivots about a first pivotal axis (axle)26, and the second finger group24pivots about a second pivot axis (axle)28.

The pivot axles26and28are connected to a body30. The biasing effect is created by springs32and34, which urge first finger group22in direction36and second finger group24in direction38. First finger group22and second finger group24define a capture zone40therebetween. When the finger groups and an object500are pushed together, the first finger group22and second finger group24are rotated away from each other thereby accepting the object500and allowing the object500to pass between the first finger group22and second finger group24and enter capture zone40, as shown inFIG. 6. Once the object500resides in capture zone40, the first finger group22and second finger group24resiliently close around the object500to retain the object500within capture zone40, as shown inFIG. 7.

In the embodiments of the invention illustrated, first finger group22includes a plurality of fingers (first finger subgroup42aand second finger subgroup42b). The second finger group24includes a thumb44. The plurality of fingers42aand42band thumb44reside in opposed relationship wherein the plurality of fingers42aand42band thumb44are curved toward one another to form a capture zone40therebetween. In the embodiments illustrated, the first finger group includes two finger subgroups. However three or four finger subgroups could also be utilized.

Now referring also toFIGS. 6–8, the plurality of fingers42aand42band thumb44cooperate to form an object handling mechanism, wherein when the plurality of fingers42aand42band thumb44and object500are pushed together with a first force FI, the plurality of fingers42aand42band thumb44are forced apart and spread away from each other allowing object500to pass into capture zone40. After passage, the plurality of fingers42aand42band thumb44resiliently close around object500. When artificial hand20and object500are pulled apart with a second force F2, plurality of fingers42aand42band thumb44spread away from each other thereby releasing object500. However, because of the construction of artificial hand20, second force F2is usually greater than first force F1. This is partially due to the “crossover” mounting arrangement of the finger groups22and24and partially due to the fact that the hooked ends of the plurality of fingers42aand42band thumb44are curved or “hooked” toward each other as hereinafter described.

Both the first finger group22and the second finger group24may be considered to have both dorsal and volar portions or surfaces. Anatomically the dorsal portion of each finger group is the backside of the finger group opposite the palm of the hand up to and including the fingernail. The volar portion of the finger group is the side of the finger group facing the palm, up to but not including, the fingernail.

With reference toFIG. 2, the dorsal portion of the first finger group22is indicated at101, while the volar portion of the first finger group22is indicated at102. The demarcation or delineation between the dorsal and volar portions101and102of the first finger group22is at the point indicated at103.

Likewise, the dorsal portion of the second finger group24is indicated at104, while the volar portion of the second finger group24is indicated at105. The demarcation or delineation between the dorsal portion104and volar portion105is at the point indicated at106.

The elements of the invention may also be considered from a geometrical point-of-view, regarding the hand20as an object-grasping device with a capture zone40for holding objects, such as the object500. An equivalent definition of the term “volar” is that the volar surfaces of the artificial hand20are the regions facing or bounding the capture zone40. All other surfaces of the hand20may be considered to constitute dorsal surfaces.

By either definition the volar surfaces102and105of the finger groups22and24, respectively, include the surfaces of the finger groups that face each other when the finger groups are closed together toward each other, as illustrated inFIG. 2. The pressing of an object against the dorsal surfaces101and104at the distal ends46and48of the finger groups22and24, respectively, does not, therefore, include the wedging of an object between the finger groups so as to pry the apart, as this would involve pressing the object against the volar surfaces102and105.

The relative movement of the first finger group22and second finger group24with respect to each other may be described in terms of relative movement about an “instantaneous axis of rotation”. An “instantaneous axis of rotation” is a mechanical engineering term meaning the momentary center of axis of rotation of a body undergoing nonlinear motion in space. In the embodiments of the invention illustrated, the respective axes of rotation of the two finger groups22and24are located at26and28, respectively, both of which are fixed relative to the body or base30. However, in some embodiments of artificial hands according to the invention the axis of rotation of one or both finger groups is not necessarily stationary relative to the base, but sometimes shifts depending upon the relative positions of the finger groups with respect to each other. Consequently, the term “instantaneous axis” may more accurately describe the “crossover” feature of the finger groups, which is an important and unique feature of the present invention as contrasted with prior artificial hands.

That is, and as is evident inFIG. 2of the application, the first finger group22and second finger group24(thumb) reside in opposed relationship with the digital ends46and48respectively thereof, curved or hooked toward one another to form the capture zone40. As is evident inFIGS. 2,6, and7, a first straight line extending between the tip of the distal end46of the finger group22and the first pivot axis26intersects a second straight line extending between the tip of the distal end48of the thumb24and the second pivot axis28. This “crossover” feature is shown inFIG. 111, which illustrates the artificial hand20with the finger groups in the same orientation as shown inFIG. 2, but with the first straight reference line extending between the tip46of the finger group22and the first pivot axis26labeled107and the second straight reference line extending between the tip of the distal end48of the second finger group (thumb)24and the second pivot axis28labeled as108. The line107passes through demarcation103while the line108passes through demarcation106. These lines107and10.8thereby “cross over” each other to define the “crossover” finger group arrangement unique to the artificial hand of the present invention.

This same “crossover” arrangement may be described in other geometric terms as well. For example,FIG. 12is a diagram that shows the first and second finger groups22and24in the same relative positions as shown inFIG. 2. As illustrated inFIG. 12, the tip46of the distal end of the finger group22, the second pivot axis28, the first pivot axis26, and the tip of the distal end48of the thumb24define the corners of a planar quadrilateral, the sides of which are labeled111,112,113, and114. As is evident fromFIG. 12, the tip of the distal end46of the finger group22and the first pivot axis26are located at mutually opposite corners of the planar quadrilateral, while the tip of the distal end48of the second finger group (thumb)24and the second pivot axis28are located at the remaining corners of the quadrilateral, which are also mutually opposite each other.

At least one of the plurality of fingers42aand42bhas a distal end which is hooked (curved) inwardly toward capture zone40. In the embodiments illustrated the distal end46of the first finger group22is hooked. Thumb44has a distal end48which is also hooked inwardly toward capture zone40. In the embodiments of the invention illustrated, at least one of distal end46and distal end48, and preferably both, are articulated so that when the plurality of fingers42aand42band thumb44and the object500are pushed together, distal ends46and48bend inwardly toward: capture zone40thereby allowing the object500to enter capture zone40, as shown inFIGS. 5 and 6. Distal ends46and48are restricted in counterrotation so that they do not bend outwardly away from capture zone40. This arrangement thereby serves to retain object500in capture zone40as shown inFIG. 8. Outward bending is prevented by stops47and49respectively on distal ends46and48, which limit opposite counterrotational movement from the finger end movement indicated inFIG. 6.

As illustrated inFIG. 6, the distal end46of the first finger group22is articulated. Therefore, when the finger group22and the object500are pushed together and toward the first and second axes26and28, the distal end46of the first finger group22flexes inwardly toward the capture zone40. This allows the object500to enter the capture zone40. Contact of the object500is with dorsal surface101.

Likewise, the distal end48of the second finger group24is also articulated. Therefore, when object500is pressed against the dorsal surface105of the second finger group24and toward the first and second axes26and28, as illustrated inFIG. 6, the distal end48of the second finger group24also flexes inwardly towardly the capture zone40. The flexure of either or both of the distal ends46and/or48of the finger groups22and24, respectively, thereby allows the object500to enter the capture zone40.

Once the object500has entered the capture zone40, as illustrated inFIG. 7, any force at all tending to withdraw the object500out of the capture zone40from between the distal ends46and48of the first and second groups22and24, will cause the articulated distal ends46and48to counterrotate away from the axes26and28about their respective axes of rotation115and116. Since there are limit stops47and49that limit the extent of counterrotation of the distal ends46and48, the distal ends46and48can counterrotate to only a limited extent.

Furthermore, a light withdrawal force opposite the direction of force F1and smaller in magnitude than force F1tends to cause the finger groups22and24to rotate toward each other due to the “crossover” finger group mounting arrangement previously described. Therefore, the finger groups22and24cannot counterrotate enough to permit withdrawal of any but the tiniest objects500. Consequently, withdrawal of an object500, as illustrated inFIG. 8, will usually require a force F2greater than the force F1necessary to insert the object500into the capture zone40.

A key aspect of the articulating distal finger ends46and48is that flexing the distal interphalangeal joints at the axes of rotation115and116in concert with the carpal joints at the axes26and28facilitates a “self-energizing” action of the hand. That is, as the object500is pushed against the dorsal surfaces of the distal finger ends46and48, the ends46and48tend to flex inwardly. The object500, with continued application of the force F1shown inFIG. 5, continues movement deeper into the capture zone40in the palm region. This gives rise to and enhances extension torque that opens the carpals, i.e., the finger groups22and24in rotation away from each other about their respective axes26and28, and thereby opens the hand20. This permits full entry of the object500into the capture zone40of the hand. The combined flexure of either or both of the distal ends46and/or48, together with the relative movement between the first finger group22and second finger group24is a unique feature of the artificial hand20.

The term “self-energizing” as employed herein, means that the force F1applied to the dorsal surfaces of the fingertips46and48, necessary to insert an object500into the capture zone40, is less than the force F2required to spread the finger groups22and24apart from each other sufficiently for the object500to be removed from the capture zone40. In contrast, a system which requires cables or some other force transmission mechanism, coupled to the muscles of the arm of the user, would not be a “self-energizing” system.

Referring toFIG. 2, a plane of object entry50, separates distal end46of said plurality of fingers42aand42band distal end48of thumb44. The object handling mechanism further includes body30. The plane of object entry50extends between the distal ends46and48of the finger groups22and24and through the body30between the axes of finger group rotation26and28. As previously noted the plurality of fingers42aand42bare pivotally connected to body30at first pivot axis26, and thumb44is pivotally connected to body30at second pivot axis28. First pivot axis26is disposed on an opposite side of the plane of object entry50from second pivot axis28. Because of this crossover axis placement, the plurality of fingers42aand42band thumb44easily spread apart to allow object500to enter capture zone40, but resist spreading apart if the object500is pulled away from the capture zone40.

As shown inFIG. 11, the “crossover” feature of finger group alignment means that the straight line107drawn between the extremity of the distal end46of the first finger group22and the axis of rotation26of the first finger group “crosses over” a second straight line108drawn between the extremity of the distal end48of the second finger group24and the axis of rotation28of the second finger group24. According to this “crossover feature” the distal end46of the first finger group22and the first pivot axis26are located on opposite sides of the plane of object entry50from each other. Likewise, the distal end48of the second finger group24and the second pivot axis28are also located on opposite sides of the plane of object entry50from each other. Moreover, the distal end48of the second finger group24and the first pivot axis26are both located on the same side of plane of object entry50. The distal end46of the first finger group22and the second pivot axis28are likewise both located on the same side of the plane of object entry50.

Again referring toFIGS. 1 and 2, thumb44pivots in a thumb plane51(FIG. 1). Plurality of fingers22includes first finger subgroup42aand second finger subgroup42b. First finger subgroup42ais pivotally connected to second finger subgroup42b, wherein the first finger subgroup42aand the second finger subgroup42bare resiliently biased toward one another. Second finger subgroup42bis pivotable about a third pivot axis27in a finger subgroup plane53(FIG. 2). The third pivot axis27is substantially perpendicular to the thumb plane51. When the first and second finger subgroups42aand42band a second object502(such as a pencil) are pushed together, the first finger subgroup42aand second finger subgroup42bspread apart from each other thereby accepting the second object502and allowing the second object502to pass between first finger subgroup42aand second finger subgroup42b(refer also toFIGS. 9 and 10). Once the second object502resides between first finger subgroup42and second finger subgroup42b, these finger subgroups resiliently close around the second object502. The biasing action is provided by spring55which is connected between second finger subgroup42band body30(refer toFIG. 1).

FIG. 4is a side elevation view showing plurality of fingers42aand42band thumb44in an open position. Plurality of fingers42aand42bhave pivoted about pivot first pivot axis26, and thumb44has pivoted about second pivot axis28.

FIG. 5is a side elevation view showing the articulated distal end of the fingers46and thumb48. Distal ends46and48bend (pivot) inwardly toward capture zone40and thereby accept object500(also refer toFIG. 6).

FIG. 6is a side elevation view of an object500and the fingers42aand42band thumb44being pushed together with a first force F1. It is noted that distal ends46and48pivot inwardly about their respective axes115and116to accept object500. For those who have a sound hand, it is common practice to use the sound hand to place or push object500into contact with artificial hand20so that the object500enters capture zone40.

FIG. 7is a side elevation view of object500residing in capture zone40between fingers42aand42band thumb44.

FIG. 8is a side elevation view of object500being pulled out of the capture zone40with a second force F2. Because distal ends46and48are hooked (curved), they tend to hold object500within capture zone40. The force F1required to push the object500into the capture zone40is therefore less than the force F2required to withdraw the object500from the capture zone40.

FIG. 9is a top plan view of a first finger subgroup42aand a second finger subgroup42bin an open position. Second finger subgroup42bhas pivoted about third pivot axis27.

FIG. 10is a top plan view of the first finger subgroup42aand the second finger subgroup42bclosed around a second object502; Second finger subgroup42bhas pivoted about third pivot axis27so that first42aand second42bfinger subgroups close about object502.

FIG. 13is a side elevation view showing thumb44being opened by a cable62. Cable62is connected to pulley64which in turn is connected to thumb44. When cable62is pulled it turns pulley64which causes thumb44to open.

FIG. 14is a perspective view of artificial hand20covered with a flexible material66to produce a realistic appearance.

FIG. 15is a side elevation of a second embodiment of the hooked distal ends46and48of the finger group22and thumb group24respectively. In this embodiment distal ends46and48are even more sharply hooked to better retain objects within capture zone40.

In terms of use, a method of using an artificial hand20for grasping an object500, comprises the steps of:(a) providing an object500;(b) providing an artificial hand20for grasping the object500, the artificial hand20comprising:a first finger group22movably connected to a second finger group24, wherein the first finger group22and second finger group24are resiliently biased toward one another;the first finger group22and second finger group24defining a capture zone40therebetween;(c) pushing the finger groups and the object500together into contact, wherein the first finger group22and second finger group24spread away from each other thereby accepting the object500and allowing the object500to pass between the first finger group22and second finger group24and enter the capture zone40; and,(d) once the object500resides in the capture zone40, the first finger group22and second finger group24resiliently closing around the object500to retain the object500within the capture zone40.

The method further including:in step (b),the first finger group22including a plurality of fingers42aand42b;the second finger24including a thumb44;the plurality of fingers42aand42band the thumb44residing in opposed relationship wherein the plurality of fingers42aand42band the thumb44are curved toward one another to form capture zone40;in step (c),pushing the plurality of fingers42aand42band the thumb44and the object500together with a first force FI; and,(e) pulling the artificial hand20and the object500apart with a second force F2, so that the plurality of fingers42aand42band the thumb44spread away from each other thereby releasing the object500, wherein the second force F2is greater than the first force F1.

The method further including:in step (b), each of the plurality of fingers42aand42bhaving a distal end46with at least one distal end46being hooked.

The method further including:in step (b), the thumb44having a hooked distal end48.

The method further including:in step (b),each of the plurality of fingers42aand42bhaving a distal end46with at least one distal end46being hooked.at least one distal end46being articulated; and,in step (c), when the plurality of fingers46and the object500are pushed together, the distal end46bending inwardly toward the capture zone40thereby allowing the object500to enter the capture zone40.

The method further including:in step (b), the distal end46not bending outwardly away from the capture zone40thereby retaining the object500in the capture zone40in step (d).

The method further including:in step (b),thumb44having a distal end48;the distal end48being hooked;the distal end48being articulated; and, in step (c), when thumb44and the object500are pushed together, the distal end48bending inwardly toward the capture zone40thereby allowing the object500to enter capture zone40.

The method further including:in step (b), the distal end48not bending outwardly away from capture zone40thereby retaining the object500in capture zone40in step (d).

The method further including:in step (b),the plurality of fingers42aand42bhaving a distal end46, and the thumb44having a distal end48;a plane of object entry50separating the distal end46of the plurality of fingers42aand42band the distal end48of thumb44;artificial hand20having a body30;plurality of fingers42aand42bpivotally connected to body30at a first pivot axis26;thumb44pivotally connected to body30at a second pivot axis28;plurality of fingers42aand42band thumb44resiliently pivotally biased toward one another; andthe first pivot axis26disposed on an opposite side of the plane of object entry50from the second pivot axis28; and,so that in step (c) because of the crossover placement of the first pivot axis26and second28pivot axis, the plurality of fingers42aand42band the thumb44easily spread apart to allow the object500to enter capture zone40.

The method further including:providing a second object502;in step (b), the thumb44pivoting in a thumb plane51, the plurality of fingers including a first finger subgroup42aand a second finger subgroup42b, the first finger subgroup42apivotally connected to the second finger subgroup42b, wherein the first and second finger subgroups42aand42bare resiliently biased toward one another, the second finger subgroup42bpivotable in a finger subgroup plane53which is substantially perpendicular to the thumb plane51;pushing the first and second finger subgroups42aand42band the second object502together;the first and second finger subgroups42aand42bspreading apart and accepting the second object502and allowing the second object502to pass between the first and second finger subgroups42aand42b; andonce the second object502resides between the first and second finger subgroups, the first and second finger subgroups resiliently closing around the second object502.

The preferred embodiments of the invention described herein are exemplary only, and numerous modifications, variations, and rearrangements can be readily envisioned to achieve an equivalent result, all of which are intended to be embraced within the scope of the appended claims. Undoubtedly, numerous variations and modifications of the invention will become readily apparent to those familiar with the construction and use of artificial hands. For example, a sensor (mechanical, electric, optical, or ultrasound) might be incorporated in the dorsal tips of the fingers to sense an object's presence, and thereby signal to a motor to open the hand to admit the object. Although addition of a sensor and a electric-mechanical activation unit would add to the complexity of the hand structure, note that it would nevertheless still provide natural, self-energizing action with minimal tasking of the user, and indeed, provide for even lower activation force and better grip, since auxiliary power is available. Accordingly, the scope of the invention should not be construed as limited to the specific embodiment depicted and described, but rather is defined in the claims appended hereto.