US2572914A - Artificial arm with elbow lock and selective control of forearm flexion or hook operation - Google Patents

Description

Oct. 30, 1951 J. D. CHAPMAN ET AL 2,572,914

ARTIFICIAL ARM WITH ELBOW LOCK AND SELECTIVE CONTROL OF FOREARM FLEXION OR HOOK OPERATION 5 Sheets-Sheet 1 Filed April 17, 1950 INVENTORS.

1951 J. D. CHAPMAN ET AL 2,572,914

ARTIFICIAL ARM WITH ELBOW LOCK AND SELECTIVE CONTROL OF FOREARM FLEXION OR HOOK OPERATION Filed April 17, 1950 s Sheets-Sheet 2 14TTO/QNEK Oct. 30, 1951 J. D. CHAPMAN ET AL 2,572,914

ARTIFICIAL ARM WITH ELBOW LOCK AND SELECTIVE CONTROL OF FOREARM FLEXION OR HOOK OPERATION 3 Sheets-Sheet 5 Filed April 1'7, 195p Patented Oct. 30, 1951 UNITED STATES PATENT OFFICE ,ARTIFIG A M W TH LB W LQ K i I SELECTIVE CONTROL OF FOREARM FLEX, 10151.01; HOOK OPERATION I Joseph D. Chapman, Inglewood, and Lawrence J.

Stevenson,

Hawthorne, Calif.,

assignors to Northrop Aircraft, I lQ-j, Hawthorne, Calif-r a corp r t on oi Califo n Application April 17, 1950, Serial No. 156,358

bya control force exerted by the amputee can bev selectively utilized to perform either of two separate and distinct functions, such'as has: heretofore required the use of two separate, independent control systems, each of which isactuated bya different muscular eiTort. The number of body motions that can be utilized to operate a prosthesis is relatively. small, and it is this factor, more than anything else, which limits thenumber of functions that can beduplicated by the pros.- thesis.

The. problem is. particularly acute in the case of artificial, arms for above-elbow amputations, owing to. the number of differentfunctions which mustv be. duplicated if a .functional arm of ma: sonablynatural action is to be had, and to the amount, of power required. by each of the several functions. For example, it; isv essential that 1 911 5108 provided for raising and lowering; the forearm, and also, for, operating the hook; both of which functions. require considerable, power, uch a can, on y be exert dby he powerfiul shoulder, back andchest. muscles. Since it is customary to. pr vide. an el ow lock in arn shcf this, type, it is also necessary to reserve one of the control motions to actuate the look, while another ont ol, mot n may b quired to, ef ect prona-r tion-supination movement of, the Wrist, and 5171111 another for flexion and extension. of the wristl. while the principlesoi the, invention are ot y was: m ted to. such use, ts advanee us. f atures are ut lized toflb st advantage. in the aboveeelbow arm, and it is another object of the invention, therefore, to provide an arti ficial arm wherein either one of any two funcions ofh rm. may be act at d at Will, Hide-- pendently of the other, by a single control mem ber.

More specifically, another object of the invention is to provide an above-elbow arm, wherein,

the control'member can be selectively connected: to the, forearm to raise and lower the same, or to theihool; tooperate the same A further object is to provide an artificial arm of the class described having an elbow lock, wherein the operative connection of the control" member to the forearm is obtained automatically when the elbow lock isunlocked, and connection to the hook is obtained automatically when the elbow is locked; the selective connection beingth-us effected by actuationof-the elbow lockitself-i 1 Another object on the invention to provide 12 Claims. (01. 3-12) an above-elbow arm wherein means is provided for flexing the forearm responsive to applicationof force b a control member, and embodyingmeans whereby the angular POSitiQIT-O-f the elbow hingeaxis can be adjusted about the upper arm centerline, so that, the planeof movement of thelower arm can be shifted to secure exact place--- ment of the hook to the mouth or other desired lateral position when the arm is fully flexed.

Another object is to provide an above-elbow arm wherein the elbow housing is shittablelongi tudinallywithrespect-to the upper arm, thereby-- enabling the upper arm to be lengthenedor shortened to fit the amputees requireinents- Still another object of the invention is to provide an above-elbow-arm embodying an elbow-- lockand a selective transien mechanism of the' type described, whichiscompact, smooth-work ing and positive action, and ofrugged, trouble free construction. These and other-'objects of the present inv'ention will become apparent to those skilled inthe} art upon consideration of the following detailed"? description of the preferred embodiment thereon" reference being hadto the accompanying draw ing's, whereim Figure 1 is a front view of an artificial arm embodying theprinciples of the invention, the arn' r being shown on the amputee so as toillustrate: more clearly the arrangement of-'- the strap'in the shoulder harness, and the connection of the controlcabletherewith; 5

Figure 2 is a rear viewofthesame; f 1 Figure 3 is an enlarged; partially cutaway side elevational viewof thearmi I Figure 4 is an enlarged cross-sectionalwiew through the elbowhousing, taken at- 4:4 in Figure 3, showing the elbow in the locked condition,'- with theco-ntrol member operati-Vel-yconnected to the-hookto-operate-thesame; Figure- 5 is a View similar to Figure 4, showing the elbowin the unlocked condition, with the control memberoper-ativelyconnected to-thef-rearm-toraise-andlower the-same;-

Figure 6 is anexploded' perspective view-'o'f the mechanism contained within the elbow-housng; Figure '7 is a sectional View through the elbcw lock, taken at 1--lin-Figu-re t; and I Figure 8' is another-sectional-view through the elbowmechanism; taken at 8--8 in Figure 5";

In the drawings; the artificial arm of myin i' vention is-seen to comprise anupperarmpo" tion l0; sometimes referred to as a stum jecting downwardly from the bottom end of the j upper arm portion I is a metal collar I3, the projecting portion of which is threaded-externally at [4 to receive the internal threads (5 of an elbow housing sleeve l6. Sleeve I6 is threaded externally at 20 to receive aclamping ring M,

and the top end of the sleeve is provided with a smooth taper 22 on its outer surface which is engaged by an inwardly tapering annular flange 23 on the ring 2|. The sleeve 16 is slit downwardly from its top end at a plurality of angularly spaced points, leaving resilient fingers '24,

and when the ring 2| is ,turned down onto the sleeve [6, the tapering flange 23 acts to squeeze. the fingers 24 inwardly, tightly clamping the sleeve to the collar l3.

Inserted up fiito the bottom end of the sleeve l6 and secured thereto by screws 25 is an elbow housing 26. The housing 26 is preferably formed of two laterally spaced halves 30 and 3|, the edges of which abut in a shiplap joint 32, as best shown in Figures 4 and 5. The bottom end of the housing is domed, or spherically rounded, and the pivot axis 33 of swinging movement between the upper and lower arm portions extends transversely through the housing 26 at the center of curvature of thebottom end thereof.

J ournaled in bushings 35 which are pressed into holes in the sides of the housing section 36, 3| concentric with the pivot axis 33 is a tubular shaft 36, and extending through the center of this tu-v bular shaft is a tie bolt 40, the head of which is recessed into a socket 4| in theouter face of a serrated plug 42. At the other end of the tie bolt is a nut 43 which is recessed into a socket 44 ina serrated plug 45, Each of the plugs 42, 45 has a tapered nose 46 which seats within a conical seat in the end of the tubular shaft 36. When the nut 43 is drawn up tight on the bolt 40, the I tapered nose portions 46 of the two plugs are drawn into the ends of the tubular shaft 36, thereby providing a tight connection between them, without any clearance or looseness.

The outer rim of each of the plugs 42, 45 is provided with serrations 50 which mesh with companionate internal serrations in holes 5| that are provided in ears 52., The ears 52 are formed integral with and project upwardly from a metal saddle 53 which is embedded in or otherwise suitably attached to the top edge of the forearm portion 1 I. The serrations 50 provide a non-rotatable connection between the plugs 42, 45 and the saddle 53, and from this it will be seen that the tubular shaft 36 is rigidly secured to the forearm portion H and is constrained to rotate therewith.

Contained within the housing 26 is an elbow lock 54, the purpose of which is to lock the forearm in any desired position so that the arm may be held in the said position without further effort on the part of the amputee. The lock is comprised of a stationary member 55 which is rigidly fixed to the housing 26, and thus to the upper arm 10; a rotatable member 56 which is fixed to the tubular shaft 36, and thus is rigidly attached to the lower arm I I and an axially slidable member 60 which is movable between a locked position, in engagement with both of the members 55,

5 6, as shown in Figure 4, and an unlocked position, in mesh with only the stationary member 55, as in Figure 5. Both the stationary member 55 and the rotatable member 55 are preferably in the form of spur toothed ring gears of the same pitch diameter and same number of teeth, while the slidable member 60 is conveniently formed of an internal ring gear to mesh with the gears 55, 56. The stationary locking gear 55 is pressed onto an annular seat at the inner end of a cylindrical boss 6| which projects laterally inward toward the center of the housing from the left hand section 30. The rotatable locking gear 56 is pressed onto the outer periphery of a radial flange 62 formed integral with the tubular shaft 36, and the slidable locking gear '60 is pressed into a seat on the inside of a drum-shaped housing 63.

The housing 63 is slidably mounted on a slightly enlarged peripheral portion 64 of the tubular shaft 36, but is constrained against rotation, of course, by the engagement of the teeth on .the internal ring gear 60 with the teeth of the stationary locking gear 55. A conical spring 65 presses against the housing 63 and sliding gear member 60, urging them to the right, as viewed in Figures 4 and 5, into the locked position of Figure 4.

To release the elbow lock 54, means is providedfor shifting the housing 63 and member 60 to the left, against the pressure of spring 65. The pre ferred lock-actuating mechanism is a cam device,v

designated in its entirety by the reference numeral 66, and consisting of a rotatable member 10 which is journaled on the tubular shaft 36. Projecting axially from the lefthand side of the T member 10 is an annular flange ll having a plurality of equi-distant, angularly spaced, sawtoothed cam faces 12 provided thereon. Each of the cam faces has an inclined slope at one side, and a relatively straight drop at the other, with a fiat crest at the top. These cam faces 12 abut against and cooperate with a companionate ring of cam faces 13 which project outwardly from the adjacent face of the housing 63, and when i the member 10 is rotated in the direction wherein the inclined slope of each cam face leaves the straight drop, the inclined slope of the cam faces 72 ride up on the inclined slopes of the cam faces 13, pushing the housing 63 to the left, until the flat crests of the cams 12 stand on top of the crests of cam 13. This is the unlocked condition shown in Figure 5. Continued rotation of member 10 carries the crests of cam 12 beyond the crests of cam 13, and the relatively straight drop in the cam surfaces then allows the spring 65 'to 5.

snap the housing 63 back to the locked condition.

The cam member ID is advanced in the proper direction by equal angular increments each time the elbow lock is to be locked or unlocked, and to this end, a ring 14 is journaled on the member 10, said ring being positioned over a circumferential groove 15 in member 10. A finger 16 is disposed down in the groove 75 and is pivotally supported on a pin 80, the free end of the spring 8|, so that it is engageable in one of a plurality of transverse grooves 82 on the inside. surface of the ring 14. When the finger 16 is thus engaged in one of the grooves 82, asshown in Figure 8, the ring 14 is enabled to drive the cam member H1 in the clockwise direction. Counterclockwise rotation of the ring'l4, however, merely causes the finger 16 to ratchet over the grooves 82, and the finger I6 is therefore nothing the groove I43 and cord channel I20'may be formed by a flat, circular ring I44, which'is se-' cured by screws I45 to the lefthand end of the pulley member l I9, as shown in Figure 4. The ring I 4| is threaded internally, and is screwed onto an externally threaded portion of the elbow lock housing 63. By virtue of this arrangement,

the pulley I I9 is tied to the axially slidablehousing 63, and is therefore constrained to move arm II, he has only to release the elbow lock 54. This is accomplished by a downward shrug of the shoulder to which the prosthesis is attached, the effect of such a shrug being to exert a pull on the control cable 83. A pull on cable 83 causes the ring I4 to rotate in a clockwise direction, as viewed in Figure 8, thereby engaging the finger I6 and driving the cam member H1 in the same direction. As the cam member revolves, the inclined faces I3 ride up the inclined faces I2, thereby shifting the elbow lock housing 63 to the left and sliding the ring gear 60 out of engagement with the locking gear 56. At the same time, the fingers I40 shift the pulley H9 to the left the same distance, thereby meshing the internal ring gear I34 with the external ring gear I33. When the elbow is unlocked, the parts are in the position shown in Figure 5, and a pull on cable I05 rotates the pulley II9, thereby raising the forearm II. 7

' To lock the elbow and operate the hook, the amputee has only to shrug the shoulder downwardly again, applying another pull on cable 83 which drives the cam member Iii through another angular increment and in the same di- 7 rection as to unlock the elbow. In this instance, however, the further rotation of cam member Ill causes the cam faces 13 to be forced into full seating engagement with the cam faces I2 by axial pressure from conical spring 65, thereby shifting the housing back to the right, and restoring the parts to the position shown in Figure 4. In so doing, the pulley H9 is shifted to the right by fingers I49, disengaging the ring gear I34 fromring gear I33 and releasing the pulley member for free rotation on the hub I ID. A pull on the cable I95 now causes the pulley H9 to rotate with respect to the forearm I I, which winds up cable I22 on the cord channel I2I and thereby pulls the hook I26 open against the resistance of the rubber band I3I. The control member I05 may be pulled either by a forward shrug of the opposite shoulder, or by swinging the stump forwardly, which has the effect of lengthening the distance between the end of the Bowden cable conduit and the point of attachment of the cable to the harness.

The connection of the elbow housing 26 to the upper arm II] by means of the threaded collar I3, split sleeve l6, and clamping ring 2I has three distinct advantages. First, it permits angular adjustment of the elbow hinge axis about the longitudinal centerline of the upper arm, whereby the plane of movement of the lower arm can be shifted to secure exact placement of the hook to the mouth or other desired lateral position when the arm is fully flexed. This is accomplished by merely loosening the ring 2| and turning the elbow housing 26 on the threaded collar I3 until the hingeaxis is positioned to secure the desired-f path of movement of the hook. The unilateral amputee may make this adjustment when fully clothed, and without removing the prosthesis.

The second advantage is that the elbow housing 26 can be screwed up or down the threads of collar I3 of the upper arm to lengthen or shorten the prosthesis to fit the amputees requirementsg and the third advantage is that the'upper arm I 0 can be quickly and easily detached from the elbow unit without the use of tools. r 1

While we have shown and described in consid erable detail what we believe to be the preferred form of the invention, it is to be understood that such details are not restrictive, and that various changes-may be made in the shape and arrange ment of the several parts without departing from the broad scope of the invention, as defined'in the appended claims We claim:

1. In an artificial arm having upper and lower arm portions connected together by an elbow joint for relative swinging movement about a pivot axis, an elbow lock comprising cooperating means attached to said upper and lower arm portions, respectively, adjacent said pivot axis for locking said arm portions against relative movement, and a hook of the open-and-close type mounted on the distal end of said lower arm portion, the combination of a pulley wheel journaled for rotation about the pivot axis of said elbow joint, a control member connected to saidpulley wheel to rotate the same, a force-transmitting member connecting said pulley wheel to said hook to operate the same when said elbow is locked and said pulley wheel is rotated with respect to said lower arm, and cooperating means attached to said pulley and to said lower arm portions, respectively, adjacent said pivot axis for lockingsaid pulley wheel against rotation with respect to said lower arm portion when said elbow is-unlocked, whereby a force applied by said control member causes said lower arm portion to be raised.

2. In an artificial arm, upper and lower arm portions connected together for relative swinging movement by an elbow joint, said elbow joint including a housing mounted on said upper arm portion, a shaft fixed to said lower arm portion and journaled in said elbow housing, a pulley wheel journaled for rotation about said shaft and movable axially with respect thereto between two positions, a tension-transmitting control cord connected to said pulley wheel to rotate the same, a hook of the open-and-close type mounted on the distal end of said lower arm portion and operatively connected to said pulley wheel, cooperating means on said shaft and on said pulley for locking the latter to said shaft when the pulley is in one of its two positions, and cooperating means on said shaft and on said elbow housing for locking said shaft against rotation with respect to said housing when the pulley is in the other of its two positions, said pulley wheel being operable, when in said one position, to raise said lower arm portion responsive to a pull exerted by said control cord, and when in said other position, to operate said hook responsive to a pull exerted by said control cord.

3. In an artificial arm, upper and lower arm portions connected together for relative swinging movement by an elbow joint, said elbow joint including a housing mounted on said upper arm portion, a shaft fixed to said lower arm portion and journaled in said elbow housing, a pulley 9 wheel journaled for rotation about said shaft and movable axially with respect thereto between two positions, a tension-transmitting control oord connected to said pulley wheel to rotate the same, a hook of the open and-close type mounted on the distal end ofsaid lower arm portion and operatively connected to said pulley wheel, cooperating means on said shaft and on said pulley for locking the latter to said shaft when the pulley is in one of its two positions, cooperating means on said shaft and on said elbow housing for locking said shaft against rotation with respect to said housing when the pulley is in the other of its two positions, said pulley wheel being operable, when in said one position, to raise said lower arm portion responsive to a pull exerted by said control cord, and when in said other position, to operate said hook responsive to a pull exerted by said control cord, another pull cord controlled by movement of the amputee, and cooperating rotary cam means operatively connected to said last-named pull cord to be rotated thereby through a predetermined angular increment each time the cord is pulled, said cam means being associated with said pulley wheel and operable to shift the latter alternately from one of its positions to the other .each time the cam is rotated through one, of said angular increments, whereby said control cord can be connected optionally to either said lower arm portion to raise the same, or to said hook to operate the same.

4. In an artificial arm, upper and lower arm portions connected together for relative swinging movement by an elbow joint, said elbow joint including a housing mounted on said upper arm portion, a shaft fixed to said lower arm portion and journaled in said elbow housing, a pulley wheel journaled for rotation about said shaft and movable axailly with respect thereto between two positions, a tension-transmitting control cord connected to said pulley wheel to rotate the same, a hook of the open-and-close type mounted on the distal end of said lower arm portion and operatively connected to said pulley wheel, an elbow lock comprising a pair of compan'ionate members arranged side-by-side, concentric with said shaft, one of said members being fixed to said housing and the other being fixed to said shaft, a third member movable axially between a locked position in engagement with both of said pairs of members and an unlocked position in engagement with only one of them, said third member being connected to said pulley, whereby the latter is shifted axially therewith, cooperating means on said shaft and on said pulley for locking the latter to the shaft when said pulley and said third member are in the position to unlock said elbow, said pulley wheel being operable to raise said lower arm portion when in one axial position or to operate said hook, when in the other axial position, and cooperating cam means associated with said third member and operable to shift the same from one to the other of its two positions.

5. In an artificial arm having upper and lower arm portions connected together for relative swinging movement by an elbow joint, and a hook of the open-and-close type mounted on the distal end of said lower arm portion, the comtbination of a rotatable and axially slidable pulley wheel disposed coaxial with the pivot axis of said elbow joint, a control member connected to said plilley wheel to rotate the same, :a tension-transmitting pull cord connecting said pulley wheel 10 to said hook to operate the same when said pulley wheel is rotated relative to said lower arm portion, an elbow lock comprising a pair of oboperating members arranged side by side on said pivot axis, one of said members being attached "to said lower arm portion to rotate therewith, the other member being non-rotatably attached to said upper arm portion, said other member being slidable axially along said pivot axis between a locked position in engagement with said one member, and an unlocked position disengaged therefrom, a cam journaled on said pivot axis and engageable with said slidable other member to shift the same between said locked and 1m- .locked positions, and to shift said pulley wheel axially therewith, and cooperating means on said pulley and on said lower arm portion for locking said pulley wheel to said lower arm portion when said slidable member is in said unlocked position, or for releasing said pulley wheel to rotate when said slidable. member is in said locked position, whereby said elbow can be locked and said hook operated by said control memben'or said elbow can be unlocked and said lower arm raised by said control member.

6. In an artificial arrn having upper and lower arm portions connected together for relative swinging movement about a pivot axis, and a hook ,of the open-and-close type mounted on the distal end of said lower arm portion, the combination of a rotatable and axially slidable pulley wheel disposed coaxial with said pivot axis, a control member connected to said pulley wheel to rotate the same, a tensiontransmitting pull cord connecting said pulley wheel to said hook to operate the same when said pulley wheel is rotated relative to said lower arm portion, an elbow lock comprising a pairof cooperating members arranged side by side on said pivot axis, one of said member being attached to said lower arm portion to rotate therewith, and the other member being non-rotatably attached to said upper arm portion, said other member being slidable axially along said pivot axis between a locked position in engagement with said one member, and an unlocked position disengaged therefrom, said slidable other member being oonnected to said pulley,whereby the latter is shifted axially therewith, a rotatable cam journa-led :on said pivot axis and engageable with said slidable other member to shift the same alternately from one to the other of its locked and unlocked positions as the cam is rotated through equal angular increments in one direction, a rotatable member coaxial with said cam and engageable therewith to advance the cam in said one direction by said angular increments when said member :is :successively oscillated, a pull cord connected to said rotatable member to oscillate the same, and cooperating means on said pulley wheel and on said lower arm portion for locking said pulley wheel to said lower arm "portion when said slidable member is in said unlocked position, orfor releasing said pulley wheel to rotate when said slidablemember is in said locked position, whereby said elbow can be locked and said hook operated by said control member, or said elbow can be unlocked and said lower arm raised by said control member;

'7. In an artificial arm having upper and lower arm portions connected together for relative swinging movement about a pivot axis, and a hook of the open-and-close type mounted on the distal end of said lower arm portion, the combination :of a rotatable and axially slidable pulley all Wheeldisposed coaxial with said pivot axis, a control member connected to said pulley wheel to rotate the same, a tension-transmitting pull ,lcord connecting said pulley wheel to said hook to. operate the same when said pulley wheel is rotated relative to said lower arm portion, an 'elbowilock comprising a pair of companionate members arranged side-by-side, concentric with said pivot axis, one of said members being fixed to said upper arm portion and the other bein fixed to and rotatable with said lower arm por tion, a third member movable axially .between a locked position in engagement with'both of said pairs of members and an unlocked position in engagement with only one of them, a spring ur ing said third member toward said locked position, means connecting said third member to said pulley, whereby the latter is shifted axially therewith, a rotatable cam coaxial with said pixot axis,

said cam having an annular ring of equidistantly spaced, axially projecting cam faces which are engageable with said third member to shift the same to said unlocked position against the pressure of said spring when the cam is in certain angular positions, and to release said thirdmembar so that the spring can return the same to said locked position when the cam is in certain other angular positions, said locked and unlocked positions occurring alternately as the cam is rotated through equal angular increments in one direction, a rotatable member coaxial with said cam and engageable therewith to advance the cam in said one direction by said angular increments when said member is successively oscillated, a pull cord connected to said rotatable member to oscillate the same, and cooperating 'means on said pulley wheel and on said lower arm portion for locking said pulley wheel to said lower arm portion when said third member is in "said unlocked position, whereby said elbow can be locked and said hook operated by said control member, or said elbow can be unlocked and said lower arm raised by said control member.

8. The device of claim '7, wherein the means for advancing said cam through one angular increment at a time comprises a rotatable ring concentric with said cam, a spring-pressed finger on said ring engageable with said cam to drive the latter in one direction, a pull cord connected to said ring to rotate the latter in said one direction, and a spring for returning said ring to its initial position when the pull on said cord is relaxed.

9. In an artificial arm of the type comprising upper and lower arm portions which are connected together by an elbow housing'and pivot shaft for relative swinging movement, and having a voluntary control hook of the open-andclose type, mounted on the distal end of said lower arm portion, the combination of a tensiontransmitting control cord, an elbow lock comprising apair of cooperating members fixed to said upper and lower arm portions, respectively, adjacent said pivot shaft for locking said arm portions against relative movement, a rotatable actuator journaled onsaid pivot shaft and shift- ,able axially thereon between two positions, said actuator being operable to lock said elbow lock and connect said control cord to said hook when in 'one'of said two positions, whereby the hook is operated when a force is applied by said control axis and shiftable axially plied by said control cord, a cam journaled "on said pivot shaft and engageable with said actuator to shift the same between said two positions, and means providing an adjustable connection between said elbow housing and said upper arm portion, whereby said housing can be turned about the longitudinal axis of said upper arm portion to secure accurate placement of said hook to the mouth or other lateral position when the arm is fully flexed, said last-namedmeans including a threaded collar fixed to the bottom end of said upper arm portion and projecting downwardly therefrom, an upwardly extending sleeve on said housing having threads on its inner and outer surfaces, and having 'slots cut into the end thereof, said sleeve being screwed onto said collar, a threaded clamping ring screwed onto the outside of said sleeve, and cooperating means on said collar and on said sleeve for constricting the slotted end of the latter, whereby said elbow housing is claimped tightly to said collar.

10. An artificial arm comprising upper and lower arm portions connected together for relative swinging movement about a pivot axis, a hook of the voluntary control type mounted on the distal end of said lower arm portion, an actuator journaled for rotation about said pivot thereon between two operating positions, a pull cord connected to said actuator to rotate the same, means connectlng said actuator to said hook to operate the same when said actuator is rotated with respect to said lower arm portion, a pair of cooperating lock members fixed to said upper and lower arm portions, respectively, adjacentsaid pivot axis, for locking said arm portions against relative movement when said actuator is in one of said positions, said actuator being then free to rotate with respect to said lower arm portion and thereby operate said hook responsive to a pull on said cord, and means on said actuator engageable with companionate means on said lower arm portion when said actuator is 'in the other of said operating positions, for locking said actuator against rotation relative to the lowerarm portion, said lower arm portion being then unlocked and free to swing relative to said upper arm portion responsive to a pull on said cord.

11. An artificial arm comprising upper and lower arm portions connected together for relative swinging movement about a pivot axis, a hook of the voluntary control type mounted on the distal end of said lower arm portion, an actuator journaled for rotation about said pivot axis and shiftable axially thereon between two operating positions, a pull cord connected to said actuator to rotate the same, means connecting said actuator to said hook to operate the same when said actuator is rotated with respect to said lower arm portion, a pair of cooperating elbow locking members fixed to said upper and lower arm portions, respectively, adjacent said pivot'axis, means shiftable by the axial movement of said'actuator for interlocking said elbow looking members, so as to prevent relative movement between said upper and lower arm portions when said actuator is in one of said positions, said actuator being then free to rotate with respect to said lower arm portion and thereby operate said hook responsive to a pull on said cord, and means on said actuator engageable with companionate means on said lower arm portion when said actuator is in the other of said operating positions, for locking said actuator against rotation relative to the lower arm. portion, said lower arm por- 13 tion being then unlocked and free to swing relative to said upper arm portion responsive to a pull on said cord.

12. An artificial arm comprising upper and lower arm portions connected together for relative swinging movement about a pivot axis, a hook of the voluntary control type mounted on the distal end of said lower arm portion, an actuator journaled for rotation about said pivot axis and shiftable axially thereon between two operating positions, a pull cord connected to said actuator to rotate the same, means connecting said actuator to said hook to operate the same when said actuator is rotated with respect to said lower arm portion, a pair of cooperating elbow locking members fixed to said upper and lower arm portions, respectively, adjacent said pivot axis, means shiftable by the axial movement of said actuator for interlocking said elbow locking members so as to prevent relative movement between said upper and lower arm portions when said actuator is in one of said positions, said actuator being then free to rotate with re spect to said lower arm portion and thereby operate said hook responsive to a pull on said cord, means on said actuator engageable with companionate means on said lower arm portion when operable t shift the latter alternately from one of it operating positions to the other each time that the said mechanism is operated, and a control cord connected to said alternator mechanism to operate the same by successive pulls.

JOSEPH D. CHAPMAN. LAWRENCE J. STEVENSON.

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

UNITED STATES PATENTS Number Name Date 2,033,150 Radtke Mar. 10, 1936 2,537,338 Fishbein et a1. Jan. 9, 1951 FOREIGN PATENTS Number Country Date 596,206 Great Britain Dec. 30, 1947

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