US2553827A - Artificial hand with articulated fingers and passively positioned thumb - Google Patents

Description

L. MASON ARTIFICIAL HAND WITH ARTICULATED FINGERS AND PASSIVELY POSITIONED THUMB May 22, 1951 Filed Oct. 27, 1948 Huazer A. Mnsau, JNVENTOR.

A7 TOQNEK 2,553,827 RS AND May 22, 1951 H. 1.. MASON ARTIFICIAL HAND WITH ARTICULATED FINGE PASSIVELY POSITIONED THUMB 4 Sheets-Sheet 2 Filed Oct. 27, 1948 INVENTOR.

May 22, 1951 H. L. MASON ARTIFICIAL HAND WITH ARTICULATED FINGERS AND PASSIVELY POSITIONED THUMB 4 Sheets-Sheet 3 Filed Oct. 27. 1948 #055271. Mnso/v,

INVENTOR.

H. L. MASON ARTIFICIAL HAND WITH ARTICULATED FINGERS AND PASSIVELY POSITIONED THUMB May 22, 1951 4 Sheets-Sheet 4 Filed Oct. 27, 1948 INVENTOR.

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ArraeA/En Patented May 22, 195 1 ARTIFICIAL HAND WITH ARTICU LATED FINGERS AND PASSIVELY POSITIONED THUlWB Hubert L. Mason, Long Beach, Calif., assignor to Northrop Aircraft, Inc., Hawthorne, Calif., a corporation of California Application October 27, 1948, Serial No. 56,866

4 Claims.

1 The present invention relates to artificial hands, and one of its general objects is to provide a new and improved hand capable of grasping and holding articles of all shapes and sizes in a manner realistically duplicating the prehension of the natural hand. A more specific object is to provide an artificial hand having articulated fingers which may be closed with an equalized force about an irregular object, together with an articulated thumb which is mechanically linked to the fingers so as to close therewith.

Another important object of the invention is to provide an artificial hand having a thumb which is pivoted for passive rotation between the adducted and abducted positions, and which is adapted to be yieldingly held in any adjusted position about its pivot axis. In this same connection, one of the features of the invention resides in the provision of a pivoted thumb which is also articulated for flexion and extension, and which is connected to the finger-closin mechanism by a novel system of linkage, whereby the thumb can be flexed and extended at an position about its adduction-abduction axis.

A further object of the invention, in one of its aspects, is the provision of a novel latch for securing the thumb in the flexed position, which is releasable by striking the back of the thumb lightly against the body or against any stationary object such as a table, chair, or the like. The advantage of this arrangement is that it enables the amputee to change the position of the thumb without requiring the use of the other hand, which is particularly desirable in the case of bilateral amputations.

The foregoing and other objects and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of two illustrative embodiments thereof, reference being had to the accompanying drawings, wherein:

Figure 1 is a partially sectioned top plan view of the preferred form of the invention, the palmar cover plate of which has been removed to show the finger and thumb actuating mechanism;

Figure 2 is a sectional view of the same, taken along the line 22 in Figure 1;

Figure 3 is another sectional view through the hand, taken along the line 33 in Figure 1;

Figure 4 is an enlarged sectional view of the mechanism at the base of the thumb, taken at 4-4 in Figure 2;

Figure 5 is a sectional view, taken along the line 5-5 in Figure 1;

Figure 6 is a partially sectioned top plan view of another embodiment of the invention;

Figure 7 is a transverse sectional view through the same, taken at 'l! in Figure 6;

Figure 8 is a sectional view taken at 8--8 in Figure 6;

Figure 9 is an enlarged sectional view of the mechanism at the base of the thumb, taken at 99 in Figure 7, showing the thumb in the closed, or flexed position; and

Figure 10 is a view similar to- Figure 9, but showing the thumb in the extended position.

The embodiment of Figures 1 to 5, inclusive, will be taken up first, and in these drawings, the

, hand is designated in its entirety by the reference numeral 5. The hand [5 is seen to comprise a base plate IE, to which a body shell I! is attached, and mounted on the body shell are articulated fingers l8, E9, and 2|, together with the thumb 22, and the actuating mechanism therefor; the construction and operation of which will be described in detail presently.

The base plate It constitutes the wrist of the hand and is preferably, although not necessarily, provided with a quick disconnect arrangement of thetype shown and described in the pending application of Gilbert M. Motis, Serial Number 24,598, filed May 1, 1948, now Patent No. 2,516,792, and entitled Quick Disconnect Coupling for Artificial Hand or Hook, to which reference may be had for full details of construction and operation. Briefly, the base plate i6 is adapted to be coupled to a oompanionate member on the distal end of a forearm component (not shown), and to this end is provided on its back surface with a rearwardly projecting, vertically extending rib 23 having straight and parallel side edges which are provided with outwardly facing flanges 2d.

A shallow, longitudinally extending slot 25 is milled out of the center of the rib 23, said slot being open at one end and preferably closed at the other end. A circular hole 26 is provided in the center of the plate It, and slidably disposed within this hole is a connector 30 which is attached at its front end to the finger closing mechanism. The connector 30 extends rearwardly beyond the bottom of the slot 25. and has a radial flange 32 on the end thereof, which is adapted to be received within a slot in the end of a coupling member (not shown) projecting forwardly from the face of an attach plate on the forearm member.

The said attachv plate is companionate to the base plate It, and is formed with channels to receive the flanges 24. The base plate H5 is coupled to the forearm member by sliding the flanged rib 23 endwise into a corresponding recess in the attach plate, and then looking the parts together, for which purpose a springpressed locking pin 33 is provided on the base plate adjacent the top end thereof. The pin 33 is slidably disposed within a cylindrical bore 34, and is urged outwardly by a spring 35 to seat in a hole in the attach plate. The locking pin 28 is adapted to be disengaged from the attach plate by means of a manually operable handle 36 which projects through a slot 37 in the end of the base plate I6.

As the base plate approaches its fully seated position, the connector 35 is engaged by the aforesaid coupling member on the attach plate, which is attached to a Bowden cable control wire extending upwardly along the arm. The control wire is attached to a shoulder harness in the usual manner, and this arrangement causes a pull to be exerted on the control wire when the harnessed shoulder is shrugged forwardly. From the foregoing it will be seen that the muscular force for operating the fingers and the thumb is transmitted to the actuatin mechanism of the hand by the connector 30, and the latter can therefore be defined as the control member of the hand, by which name it is identified in the claims.

Projecting forwardly from the base plate It around the outer edge thereof is a flange 33 to which the body shell I! and a palm cover shell 39 are attached by means of fiathead machine screws. The body shell I! constitutes the back half of the hand, and is preferably formed of heavy gage sheet aluminum or other light metal. The fingers I8, I9, 253 and 2! may be of any desired construction and, as shown herein, each comprises two generally tubular sheet metal sections 45 and 4! which are pivotally joined together by a pin 42. The base ends of the inner section 49 of fingers I8 and I9 are pivotally mounted on a shaft 43, while fingers 20 and 2! are pivotally mounted on another shaft 44; the axes of said shafts being disposed at an angle to one another so that the fingers I8 and I9 tend to spread apart from fingers 2c and 2! when extended, and to come together when closed. The outer ends of the shafts 43 and 44 are received within holes in the opposite side walls of the body shell I1, and the inner ends thereof are supported by a central block 45 which is formed on a bracket member 45 mounted on the body plate I'I.

Extending longitudinally through the inner sections of the fingers are links 5!], the outer ends of which are attached by pins 5! to the outer finger sections 4! above the pivot pins 42 (Figure 3), and the inner ends of which are attached by pins 52 to bracket 53 mounted on the body shell II. Pins 52, it will be noted, are located below the pivot shafts 43, 44, which is opposite to the disposition of pins 42, 5!. Link 5!! therefore crosses a line connecting the centers of pins 42 and shafts 43 or 44 and by virtue of this arrangement, the outer finger section 4! is pulled inwardly, or in a counterclockwise direction, about its pivot 42 when the inner section 40 is swung upwardly about its supporting pivot shafts 43, 44.

Ears 54 project upwardly from the inner finger section above the pivot shafts 43, 44, and connected to these ears by pins 55 are rearwardly extending links 56, 56. The rear ends of the links 55 for fingers I8 and I9 are connected by pins Bi! to the opposite ends of a transversely disposed equalizer bar 6!, while the links 55' for fingers 20 and 2| are connected by pins 52 to another equalizer bar 63. The equalizer bars 6! and 63 are connected at their midpoints by pins 64 and 65 to links 56 and 6?, said links extending rearwardly from the equalizer bars and being connected by pins I6 and I! to lever arms '12 and I3.

Lever arm I2 is formed integrally with and projects upwardly from a transverse shaft 14 adjacent one end thereof. The ends of the shaft 14 are journallecl for rotation in bushings I5 and I6 which are mounted in bearing support blocks l1 and 78, said blocks being secured to the opposite side walls of the body shell ll by fiathead machine screws. The shaft is supported at its midpoint in another bushing which is mounted in the bracket member 45.

The portion of shaft 14 lying on the side of bracket 45 opposite the lever arm '!2 is reduced slightly in diameter, and mounted side by side on this reduced portion is a gear sector 8! and sleeve 82. The lever arm I3 is formed integrally with the sleeve 82 and projects upwardly therefrom substantially parallel to lever arm I2. Sleeve 82 and gear sector 8! are fixedly secured to the shaft I4 by pins 83 and 54, and therefore rotate as one with the shaft.

Meshing with the teeth of gear sector 8! is a worm 85 which is rotatably mounted on an axle 86 projecting upwardly from the base of bracket 46. A pinion 95 is rigidly connected to the worm at the upper end thereof, and meshes with a rack 9i extending lengthwise of the hand. The back surface 52 of rack 5! is smooth and fiat, and bearing on this surface directly across from the pinion 90 is a roller 93 turning on an axle 94. The purpose of the roller 93 is to back up the rack 9! and hold the latter in mesh with the pinion 95, while at the same time permitting free longitudinal movement of the rack.

The roller 93 and its axle 94 are supported on a bracket 95, the top portion of which includes a shelf 98 extending laterally across the top of rack 9! and pinion 9B. The axle 86 for the worm 85 and pinion 30 extends through a hole in the shelf 95 and has a nut 9! screwed onto the projecting threaded end thereof. The bottom edge of the rack 95 is slidably supported on another ledge 98 projecting laterally from the bracket 95, and the rack 9! is thus confined against movement relative to the pinion 95 in the axial direction thereof. Another roller 99 turning on a tubular axle I05 alongside the roller 93, also runs on the back surface 52 of the rack, and provides directional stability for the rack. The rack 55 is yieldingly urged outwardly, or to the right, as seen in Figure 1, by a spring I5 I, one end of which is anchored to the block 45, and the other end being attached to the outer end of the rack.

Formed on the rear end of rack 9! is a box I52 which is fixedly connected to an arm I53 projecting obliquely from the connector 3!). The rack 9! is thus joined directly to the connector 30 and moves with the latter as though it were an integral part thereof. One end of a pivoted lever I84 projects into the space between the top and bottom sides of the box I92 and is connected thereto by a pin I65, said pin passing through a longitudinally extending slot I06 in the lever. The lever I94 is swingably supported on a pivot pin Hi3, and its other end is connected by a pin I I I to a clevis I I 2 screwthreaded on the rear end of a push rod I I3.

The push rod II3 extends forwardly through the pivot center of a supporting structure I I4 for the thumb 22, and is connected at its front end to the thumb actuating linkage. The thumb-supporting structure I I4 consists of a base II5 which is secured by flathead machine screws to the body shell I1, and formed on the upper end of. said base is a circular plate I I6 having a tapped hole I through its center, as shown in Figure 4. An adjusting screw I2I is threaded through the hole I20, and is secured against turning by a set screw I22. The center of the screw I2I is drilled to provide a hole I23, through which the push rod II3 passes.

Threaded onto the front end of the screw I2I is a radially flanged bearing member I24, upon which is swiveled a turntable I25. The turntable I comprises a circular plate I26 having a central aperture in which the bearing member I24 is received, said aperture being recessed around its outer edge to provide a seat for the thrust flange I21 of the bearing member. A cylindricalproject into the hollow base section I32 of the thumb 22 and are connected therewith by a pivot pin I33. Extension arms I34 project obliquely forward from the outer ends of the bracket arms I3I, and these are drilled to receive a pin I35 which serves as an axle for certain elements of the thumb-actuating linkage, which will be taken up in detail presently.

The swiveled plate I26 is spaced a short distance out from the stationary plate H6, and disposed within the space between them is a dished spring friction member I36 having a central aperture through which the adjusting screw I2I passes. ber I36 bears against the stationary plate H6, and the outer edge portion thereof bears against the adjacent surface of the swiveled plate I26.

The bearing member I24 is adapted to be tightened down on the screw I2I by means of a spanner wrench (not shown), causing the friction member I36 to be compressed between the plates I I 6 and I 26. The frictional resistance to rotation of plate I25 relative to plate H6 is proportional to the bearing pressure of the member I36 against the plates; hence, the tighter the memberv I36 is compressed, the greater is the resistance, and the more firmly the thumb is held in its angularly adjusted position about the pivot axis.

Pivotally connected by a pin I40 to the outer end of the base section I32 of the thumb is an outer section I4I, which is likewise formed of sheet metal. A link I42 is attached at one end by a pin I43 to the outer thumb section I4I adjacent the pivot I40, and the other end of the link is connected by a pin I44 to one arm of a bell crank I45 which is rotatably supported on the pin I35 between the extension arms I34. In the illustrative embodiment, the bell crank I45 is made up of two laterally spaced side members which are joined together to rotate as one about the pivot I35. Rigidly fixed to the bell crank I45 between the side members is a gear sector I46 which meshes with another gear sector I50. Sector I50 is pivotally supported on the pin I33 between the bracket arms I3I, and is connected to the thumb section I32 by a pin I5I, so that the thumb is constrained to rotate with the sector I50.

The other arm of the bell crank I45 projects laterally inward toward the center of the hand,

The center portion of the friction memand is connected by a pin I52 to a bracket I53 projecting radially from a sleeve member I54 on the push rod H3. The sleeve member I54 is free to rotate on the push rod, but is confined against axial movement with'respect thereto by, a radial flange I55 on the push rod which engages one end of the sleeve. The other end of the sleeve is engaged by a nut I55 which is screwed onto thread I50 on the end of the push rod.

The fingers and thumb are pulled closed, or flexed in prehension, when the connector 30 is pulled rearwardly by a shrug of the harnessed shoulder. Such rearward movement of the connector 30 causes the rack 9| to move rearwardly with it, which drives the pinion 90 and worm 85. Rotation of the worm drives the gear sector 0! and shaft 14 in a counterclockwise direction. as viewed in Figure 3, thereby swinging the two lever arms i2 and 13 rearwardly. Links 65 and 51 are carried rearwardly with the lever arms 12, 13, and the tensile force transmitted by each of the links is distributed equally by the equalizer bars BI, 63 to the fingers to close the same.

Rearward movement of the rack 96 also causes the lever I04 to rock in a counterclockwise direction about its pivot IIO, which causes push rod II3 to be pushed forwardly through the thumbsupporting structure H4. Forward movement of the push rod I I3 rocks the bell crank I 25 and gear sector I46 in a clockwise direction, which drives the gear sector I50 in a counterclockwise direction to close the thumb.

The thumb 22 is adapted to be moved to any desired position about the pivot axis of the rotatable plate I26 between the adducted position, shown in phantom lines in Figure 2, and the abducted position, shown in solid lines in Figure 2.. This pivot axis thus represents the adduction-- abduction axis of the thumb; while the pivot pin I33 represents the fiexion-extension axis of the thumb. The thumb is yieldingly held in its angularly adjusted position about the adductionabduction axis by means of the friction member I36, and the amount of frictional resistance to rotation of the thumb is determined by the extent to which the friction member is compressed.

The other embodiment of the invention, shown in Figures 6 to 10, inclusive, is generally similar in construction to the previously discussed embodiment, and parts that are similar to those already described are given the same reference numerals with the suffix a. The finger-closing mechanism differs from that of the previous embodiment in that the shaft 14a is provided with an upwardly extending arm 510 which is connected by a pin I1I to the front end of a link I12. The rear end of the link 512 is provided with a clevis I13 which receives a tongue 414 projecting forwardly from the end of the connector 300., and is connected therewith by a pin I15. A spring H3 which is anchored at one end to the bracket 53a of finger 20a, is attachedat its other end to arm I10 and exerts a Dull thereon tending to restore the fingers to the normally extended condition shown in the drawings.

When the connector 30a is pulled rearwardly by a shoulder shrug, the shaft 14a is rocked in a counterclockwise direction, as viewed in Figure 8, drawing the fingers ciosed with an equalized pull. When the force on the connector 30a is relaxed, the shaft 14a is rocked back to its initial position by the spring I16, opening the fingers out to the extended position.

The thumb 22a is swiveled for rotation about the adduction-abduction axis between the two 7 positions shown in Figure '7, and is pivoted also for swinging movement about the fiexion-extension axis, represented by the pin 133a. The thumb itself, however, is made in one piece, without the joint shown in the preceding embodiment, and is not adapted to be closed by the operation of the connector 3%. Instead, the thumb is passively changed from the extended position shown in Figure to the flexed position shown in Figure 9, and is releasably held in the latter position by latching mean which will be described presently.

The thumb 22a is supported on a stationary standard I88 which is fixed to the body shell Ha,

and formed on the upper end of the standard is a circular boss |8i having a central hole I82. Extending through the hole E82 is a bolt I83, the threads of which are screwed into a tapped hole I84 of a rotatable member 185. Interposed between the head lts of the bolt 1&3 and the adb jacent face of the stationary boss I8! is a resilient friction disk I933 of cork or like material, while another friction disk 95 is interposed between the adjacent faces of the rotatable member H and stationary boss lei When the screw I83 is tightened, the disks H98 and i9! are compressed, increasing the frictional resistance to turning of the member 35 with respect to member [8 i.

Laterally spaced bracket arms I92 project radially outward from one side of the member I85, and pass on opposite sides or" the thumb 2211; the ends of pivot pin I33a being received within holes in the said arms. A torsion spring 21! is wrapped around the pin 533a and one end thereof is anchored at 2 i 2 in the member 585. The other end of the spring bears against the thumb 22a urging the latter outwardly toward the extended position shown in Figure 10.

The thumb is adapted to be latched in the flexed position shown in Figure 10, and to this end is provided with a catch 193 which is secured by rivets 594 to the thumb. A lip i9?) on the outer end of the catch i933 is adapted to be engaged by another lip we on a detent 253, and when thus engaged, locks the thumb in the flexed position until the lip 9 3 is disengaged from lip Extending through a hole in detent 255 and projecting laterally from opposite sides thereof is a pin 28%, the ends of which are slidably disposed within slots 262 in bracket members 199, said bracket members being formed integrally with the member 585 and projecting from one end thereof. A leaf spring 2% is secured to the member I85 by pressed-in rivets 255, and a rolled lip 204 on the spring bears downwardly against the top of the detent 295.

When pin 231 is at the bottom of slot 202, the spring lip 2M engages the detent Ziill above the pin, exerting a counterclockwise torque on the detent. When pin 2M is at the top of slot 202, the spring lip 26:? engages the detent below the pin and exerts a clockwise torque thereon. A limit stop pin 2% limits the counterclockwise rotation of detent 28b to the position shown in Figure 10.

If the thumb and latch detent are in the positions shown in Figure 10, the thumb is closed to the flexed position and locked in place by merely striking the back of the thumb lightly against the body, or any convenient object such as a table top, chair, or the like. As the thumb swings upwardly, or counterclockwise about pivot l33a, the end of catch I95 engagesa shoulder! Ill-on detentifiil, pushing the latter inwardly until pin 20! reaches the top of slot 202. At this point, the spring 263 urges the detent down into engagement with the catch, with the result that the lip see remains interlocked with lip 195 when the presur-e is removed from the back of the thumb. Spring 2!! now pulls the thumb out to the position shown in Figure 9, with pin 20] at the bottom of slot 2&2. The interlocking engagement of the lips I95, 19-3 prevents the detent 2% from yielding to the spring 293 and swinging about pin Ziii to the limit stop 2%. However, the next time that pressure is applied to the back of the thumb, the lip is disengaged from lip 55 and detent 2E3?) snaps back against the limit stop. The advantage of this arrangement will be readily apparent to those skilled in the art, since it enables the amputee to change the position of the thumb without using the other hand or hook.

While I have shown and described in consider able detail two illustrative embodiments of my invention, it is to be understood that such details are not restrictive, and that various changes may be made in the shape and arrangement of the several parts without departing from the broad scope of the invention, as defined in the appended claims.

I claim:

1. In an artificial hand, the combination of a plurality of articulated fingers and an articulated thumb, said thumb being swiveled for rotation about an adduction-abduction axis, a forcetransmitting control member, linkage means operatively connected to said control member for closing said fingers with an equalized force, and for closing said thumb, said linkage means for closing said thumb including an axially movable push rod disposed coaxial with the swivel axis of the thumb.

2. In an artificial hand, the combination of a plurality of fingers and an articulated thumb, said thumb being swiveled for rotation about an adduction-abduction axis, a force transmitting control member, linkage means operatively connecting said control member to said thumb for ciosing the same, said linkage means including an axially movable push rod disposed coaxial with said adduction-obduction axis, and a member journaled on said push rod for rotation about the axis thereof but constrained against axial movement with respect thereto, said member being connected to a portion of said linkage means mounted on said thumb and rotatable therewith, whereby said thumb can be closed by said linkage means in all positions about said adduction-abduction axis.

3. In an artificial hand having a plurality of fingers and a :thumb, the combination of a thumb-supporting plate swiveled on said hand for rotation about an adduction-abduction axis, said thumb being pivotally supported on said plate fcrswinging movement about a fiexion-extension axis, a force transmitting control member, linkage means operatively connecting said control member to said thumb for swinging the same about said flexion-extension axis, said linkage means'including an axially movable push rod extending through said plate coaxial with said adduction-abduction axis, a gear sector fixed to said thumb concentric with said fiexion-extension axis, another gear sector pivotally supported on said plate-and -meshing with said first-named sector, anda-lever arm fixed to said last-named sector and-connected to said push rod, whereby axialmovementof -said push rod causes said lastarticulated fingers and an articulated thumb, a 5

force-transmitting control member, a longitudinally movable rack connected to said control member, a rotatable pinion meshing with said rack, a worm fixedly connected to said pinion to rotate therewith, a gear sector meshing with said worm, said gear secto-r being fixedly mounted on a transversely disposed, rotatable shaft, a pair of arms projecting from said shaft, forwardly extending links connected to said arms, each of said links being connected to the midpoint of an equalizer bar, and other links connecting the two ends of each equalizer bar to two of said fingers, whereby an equalized force is transmitted to the two fingers associated with each equalizer bar, and means connected to said control member for closing said thumb simultaneously with said fingers.

HUBERT L. MASON.

REFERENCES CITED 'The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 760,102 Carnes May 1'7, 1904 1,046,966 Carnes Dec. 10, 1912 1,324,564 Pringle Dec. 9, 1919 15 2,464,577 Hobbs Mar. 15, 1949 FOREIGN PATENTS Number Country Date 345,340 Great Britain Mar. 20, 1931

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