Auxiliary Device For Hand Prosthesis

Abstract

A device for assisting in the holding of elongated bodies and small articles, for use with a hand prosthesis (artificial hand) comprises a band-type spring urging apart an upper and a lower member, one of which is engaged by the thumb while the other is engaged by the index finger and middle finger of the artificial hand. The upper member has a web received between these fingers. A pair of pincer-type extensions project from the upper and lower members.

Description

FIELD OF THE INVENTION

My present invention relates to prosthetic hands and, more particularly, to an auxiliary device adapted to be used with an artificial hand to facilitate the gripping of small articles or articles difficult to retain with a conventional mechanical hand or hand prosthesis.

BACKGROUND OF THE INVENTION

While a variety of hand prostheses have been proposed with drives and operating mechanisms of various types, considerable difficulty is still encountered in the use of a prosthetic hand in the picking up, gripping and positioning of small items and various articles, such as pencils, pens, . . . , of a round or other nonpolygonal cross-section.

For the most part a hand prosthesis comprises an opposable thumb of a rigid construction which may be movable together with the fingers or may be fixedly positioned to function as a countermember against which the fingers are displaced. Even the fixedly positioned thumb may have a number of positions in which it may be locked.

The fingers generally include an index finger and a middle finger of similarly rigid construction although various movable joints may be provided. However, with most artificial hands of this type, it is not possible to draw the tips of these fingers or the thumb inwardly to any significant extent and hence it is difficult to grip or engage relatively small items such as pins, paper clips and the like. Furthermore, since the contracting faces of the fingers and thumbs of the hand prosthesis, regardless of the operating mechanism, are curved, they tend to contact elongated and round objects, such as pencils and pens at only one point at each finger. As a consequence the object is held insecurely and it is difficult for the prosthesis wearer to write with the object or otherwise manipulate it in a convenient manner. In certain systems, it is possible to lock an elongated object between the shanks of the fingers but here too manipulation is difficult.

In order to overcome these disadvantages, it has been proposed to modify the surfaces of the thumb and finger tips to provide greater gripping power. As a consequence, certain object shapes may be gripped more effectively while the engagement of others remains difficult. In all cases, for the most part, it is most difficult to engage thin, small and sheet-like objects with conventional prosthetic hands.

The term "prosthetic hand" as used herein, is intended to identify an anthropomorphic prosthesis having at least the two movable fingers and an opposed thumb mentioned earlier. These prosthetic hands may be driven mechanically, e.g., via a cable operating against a spring urging the fingers away from the thumb or drawing the fingers and thumb together against the force of a spring, worm-wheel arrangements driven by cable, or by some other source of power, electric, pneumatic and hydraulic motors and like conventional means.

OBJECTS OF THE INVENTION

It is the principal object of the present invention, therefore, to provide an improved device for assisting in the manipulation of a prosthetic hand whereby the aforementioned disadvantages can be avoided.

Another object of the invention is the provision of an improved prosthetic device enabling the gripping and manipulating of articles which have been in the past difficult to hold and manipulate with conventional prosthetic hands.

SUMMARY OF THE INVENTION

The above and other objects are attained, in accordance with the present invention, which provides a device for use in conjunction with a prosthetic hand and comprises a pair of juxtaposed members having confronting surfaces and respectively engageable behind these surfaces by the thumb of a prosthetic hand and the opposed index and middle finger, respectively, the juxtaposed members being interconnected by a band-type spring urging the members apart and having a bight lying proximal to the palm of the prosthetic hand. According to an important feature of the invention, the finger-engaging member is provided with a web extending between the index and middle finger and extending longitudinally therealong.

More specifically, the invention comprises a device receivable within the prosthetic hand which has, as specified above, a pair of fingers in close justaposition, corresponding to and hereinafter identified as the index finger and the middle finger, and a thumb opposed thereto, the thumb having its normally convex surface confronting the convex tips of the index and middle finger and usually positioned such that, when the thumb and fingers are brought together, the tip of the thumb lies between the finger tips.

The device of the present invention thus comprises a pressure plate, constituting the web-carrying member mentioned earlier, against one side of which the tips of the index and middle finger are brought to bear and a counter-pressure plate whose rear surface rests against the tip of the thumb, the two plates being essentially parallel and being shiftable against the force of a band-type spreading spring toward and away from one another to provide a clamping action between the plates. The pressure plate engaged by the index and middle finger, according to the invention, is formed with the rearwardly projecting web which lies in a plane generally perpendicular to the plane of the pressure plate and preferably extends longitudinally between the aforementioned fingers. Preferably respective extensions project forwardly from the pressure plates in a parallel relationship and form pincer tongues which cooperate to enable the device to grip small articles.

According to yet another feature of the invention, the web-carrying member extends inwardly (with respect to the hand) of the pressure plate in a roof or canopy configuration in at least two angle portions rising at an obtuse angle from the pressure plate and thereupon bent downwardly at an obtuse angle to conform approximately to the inner configuration of the fingers, the web extending along the canopy toward the knuckle joint of the fingers. The outer edge of the web may be curved with an approximate convex curvature of the outer surfaces of the fingers so that it projects only limitedly therebeyond if at all. At its end proximal to the knuckle joint, the web may be perpendicular to the canopy portion of the web-carrying member.

According to another feature of the invention, at least one of the confronting surfaces of the pressure plates is planar while the other is of V-cross-section including acute angles with the planar surface in a closed condition of the device, the inclined surfaces being symmetrical with respect to the median plane through the device whereby the latter may be used equally effectively for both right-hand and left-hand prosthesis. Furthermore, at least one of these surfaces is provided with at least one linear guide channel preferably inclined to this plane and thus adapted to receive a round object such as a writing instrument, and enabling the same to be held with greater security than heretofore. It has been found to be advantageous to provide two such inclined channels of generally flat curvature, to again permit the device to be employed for left-hand and right-hand prosthesis interchangeably.

According to yet another feature of the invention, the pressure plates are each constituted unitarily of a synthetic resin, by molding or casting and the band-type spring is inserted into the one piece pressure plates by molding or during casting so that a firm attachment is provided.

DESCRIPTION OF THE DRAWING

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description reference being made to the accompanying drawing in which:

FIG. 1 is a side-elevational view of the device of the present invention in a prosthetic hand;

FIG. 2 is an end view of the device;

FIG. 3 is a bottom view of the upper pressure plate;

FIG. 4 is a cross-section taken along the line III -- III of FIG. 1; and

FIG. 5 is a cross-section taken along the line V -- V thereof.

SPECIFIC DESCRIPTION

In FIGS. 1 - 3, I show a hand prosthesis which includes an index finger 1 adjacent a middle finger 2 and opposed to a thumb 3, the fingers 1, 2 being urged toward the thumb 3 by a motor represented diagrammatically at M in the hand and operating against the diagrammatically represented spreading spring 4. The palm of the hand is represented at 20. The device of the present invention comprises a pressure plate 5 formed integrally and unitarily and an upwardly angled coping portion 6 including an obtuse angle .alpha. with the pressure plate 5 against which the tips of the index finger 1 and middle finger 2 rest. The linearly extending coping portion 6 follows the line of the inner face of the fingers 1, 2 and terminates in a downwardly angled coping portion 7 forming the obtuse angle .beta. with coping portion 6. The coping portion 7 thus lies along the corresponding portion of the fingers 1, 2. The unitary molded synthetic-resin web-carrying member 5, 6, 7, is formed centrally with an upstanding longitudinally web 8 received between the fingers 1, 2 (see FIG. 2) and running the full length of this upper member. The upper or outer surface 8' of the web corresponds in curvature to the outer portions of the fingers 1, 2 and terminates in an end flank 8" which is substantially perpendicular to the coping portion 7 and the outer flank 8' while lying approximately at the junction of the two fingers.

The plate 5 thus comprises a generally planar member whose reverse surface 5' is engaged by the convex tips of the fingers 1, 2 and whose obverse surface 5" is likewise planar and is juxtaposed with a counterpressure plate represented generally at 11. The surface 5" is formed with a pair of mutually intersecting channels 13 which are inclined to the median plane of symmetry P (see FIGS. 3 and 4) at angles .gamma. of about 30.degree., the channels having a shallow depth d (FIG. 2) which is less than their width w (FIG. 3) to enable round objects such as pencils to be held with ease. Since the channels run symmetrically to opposite sides of the median plane, and are diagonal with respect to the generally rectangular pressure plate, the device may be used interchangeably for right- and left-hand prosthesis.

The counterpressure plate 11 (best seen in FIGS. 1, 2 and 5) has outlines coextensive with those of pressure plate 5 but is of triangular profile. The surface 11" of the counterpressure plate 11 juxtaposed with pressure plate 5 is subdivided into two portions 11a" and 11b" which are inclined symmetrically with respect to the median plane P away from the surface 5" at a relatively small acute angle .delta. of about 15.degree.. The apex 11c" is a rounded ridge. The underside 11' of this pressure plate is engaged by the convex tip of the thumb 3 and is generally planar.

The members 5, 6, 7 and 11 are joined together by a bent band-type spring 9 whose bight lies close to the palm 20 of the prosthesis (FIG. 1) and whose shanks 9a and 9b are embedded in the two members by pressing, casting or molding as previously described. The pressure plates 5 and 11 are provided with respective pincer tongues 10 and 12 at their forward faces, the tongues being composed of stainless spring steel and being pressed or embedded in the synthetic-resin bodies 5 and 11. The tongue 10 is inclined somewhat downwardly and is rounded at its end (FIGS. 2 and 3) while the tongue 12 is similarly rounded but is upwardly dished.

Claims

I claim:

1. A device for assisting the gripping of diverse objects in a prosthetic hand having index and middle fingers and a thumb opposed thereto, said device comprising a first pressure plate engaged along one side by said fingers and a second pressure plate juxtaposed with said first pressure plate and engaged along one side of said second pressure plate by said thumb, said pressure plates having confronting surfaces, a band spring interconnecting said pressure plates, and a longitudinally extending web formed on said first pressure plate and received between said fingers.

2. The device defined in claim 1, further comprising angle coping portions connected to said first pressure plate and extending along respective inner portions of said fingers, said web extending along said coping portions.

3. The device defined in claim 2 wherein said web has a curved outer edge conforming generally to the configuration of outer portions of said fingers.

4. The device defined in claim 3 wherein at least one of said confronting surfaces is formed with a pair of intersecting channels substantially symmetrical with respect to a median plane through said plates and said web.

5. The device defined in claim 4 wherein said coping portions, said first pressure plate and said web are formed unitarily with one another.

6. The device defined in claim 5 wherein said spring has ends embedded in members respectively forming said pressure plates.

7. The device defined in claim 6 wherein at least one of said confronting surfaces is generally planar and another of said confronting surfaces is symmetrically inclined relative to the planar confronting surface outwardly with respect to said median plane.

8. The device defined in claim 7, further comprising a pair of pincer-forming tongues respectively received in front faces of said pressure plates and projecting therebeyond.

9. The device defined in claim 8 wherein one of said tongues is dished in the direction of the other of said tongues.

10. A prosthetic device comprising a prosthetic anthropomorphic hand having a pair of generally codirectionally extending but spaced-apart fingers corresponding to an index finger and a middle finger respectively, a thumb opposed to said fingers, and means for displacing said fingers and said thumb relatively; and a unit received in said hand and comprising a first member engaged by said fingers, a second member engaged by said thumb and a band spring interconnecting said members while urging same apart, said first member being formed unitarily with a pressure plate having a generally planar reverse side engaged by the tips of said index finger, respectively, a first coping portion extending at an obtuse angle from said first pressure plate along an inner portion of said fingers, and a second coping portion inclined at an obtuse angle to said first coping portion while extending along an inner portion of said fingers, and a longitudinally extending web rising from said first pressure plate and said portions and generally perpendicular thereto along a median plane of symmetry of said members, said web having an outer curvature corresponding substantially of said fingers while extending the full length of said first member, said first pressure plate having a surface confronting said second member and formed with a pair of diagonally intersecting channels symmetrical with respect to said plane, said second member having a surface confronting said first member and inclined in opposite directions symmetrically away from said plate.