US 2537338 A
Description (OCR text may contain errors)
Jan. 9, 1951 M. FlsHBElN TAL ARTIFICIAL ARM 2 Sheets-Sheet 1 md nay n.13, 1947 Jan. 9, 1951 M. FlsHBElN ErAL ARTIFICIAL ARM 2v Sheets-Sheet 2 Filed lay 13, 1947 'elbow amputations.
Patented Jan. 9, 1951 ARTIFICIAL ARMl Meyer Fishbein, Los Angeles, and Michael J. Nagy and Donald M. Threewit, Inglewood, Calif., assignors to Northrop Aircraft, Inc.,-Hawthorne, Calif., a corporation of California Application May 13, 1947, serial No. 747,690,
The present invention relates generally to prosthetic devices, and is more specifically concerned with articial arms for use in above-the- The primary object of the invention is to provide a new and improved elbow joint with a locking device therefor, whereby the forearm can be locked with respect to the upper arm in any one of a large number of closely spaced angular positions within the range of its movement.
Another object of the invention is to provide an elbow locking device which is adapted to be locked and unlocked by successive downward and forward shrugs of the shoulder, thereby eliminating the operating button provided for that purpose in certain prior artificial arms. The ob- J'ection to such operating buttons is that they must be pressed or tapped against the body or some other object in order to lock or unlock the elbow, which is sometimes difficultor inconvenient to do when the arm is in certain positions. Further, the act of pressing the button to actuate the lock, and the audible tap which usually accompanies it, draws attention to the wearer's physical handicap and is a source of embarrassment. With the present invention it is possible, by an almost imperceptable shrug of the shoul der, to operate the lock with the arm in practically any position, and the wearer is thus enabIed-to perform feats which would otherwise be impossible to accomplish.
Another object of the invention is to provide an elbow joint having a positive locking device, and also embodying friction clutch means permitting the forearm to slip under overload 'jury to the wearer.
Still a further object of the invention is the provision of an elbow joint which is attached to the upper arm or stump socket by a frictionally/ resisted swivel connection so that the hinge axis can be turned to give any desired plane of movei ment to the forearm.
The foregoing and other objects and advanthose skilled in the art upon consideration of the following detailed description of the preferred embodiment thereof, reference being had to the l* accompanying drawings, in which;
ends Y to the' shoulder member through a ring 2i) which is attached by a strap 2| Figure l is a perspective view, taken from behind and to one side, of the artificial arm of the invention, showing the manner in which it is worn and the harness for actuating the several mechanisms thereof g Figure 2 is an enlarged side elevational view of a portion of the same;
Figure 3 is a sectional view taken along the line 3 3 of Figure 2, showing the locking device in its locked condition;
Figure Ll is another view of the same, showing the device unlocked;
Figure 5 is a sectional view taken along the line 5-5 in Figure 3;
Figure 6 is an exploded. view of the elbow assembly; and
Figure 'l is a perspective view of the invention from the front.
In the drawings, the artificial arm comprises an upper arm or stump socket Iii and a forearm shell II having a hook 9 mountedon the lower end thereof.v The forearm shell lI is connected to the stump socket l0 by the elbow mechanism of the invention, which is designatedin its entirety by reference numeral l2.
Both the stump socket I@ and forearm shell II are preferably formed of plastic-impregnated fabric such as, knit cotton stockinet which is drawn over forms and cured in an oven, giving a rigid, lightweight shell of considerable strength and'rigidity. In the case of the stump socket I0, the upper end of the form is made from a cast taken of the stump so as to obtain an accurately formed impression of the stump and thereby insure a comfortable it The stump socket Ill is held in place on the stump by means of a harness I3 comprising a pair of shoulder members I4 and I5 which are connected across the chest by a strap I1. A strap loop I6 is connected at its I4 and passes to the stump socket Ill on the outside thereof. A second strap'22 is also secured at its ends to the shoulder member I4 and passes through another -ring (not shown) on the inside of the stump socket'l. VThe two straps I6 and 22 slide freely through their respective rings on the stump socket and hold the latter in place on the stump while at the same time permitting the shoulder .35, to withstand ordinary loads.
,shell I8; being assembled with the latter at the time the stockinet material is formed Yover the mold and cured in the oven` Attached to the turntable 25 is a housing 21 which is divided on its median plane into two halves 28 and 29 having cooperating annular flanges 38 on their abutting edges which are telescopically fitted together to form an interlocked assembly. The base portions of the housing sections 28. 29 are each provided with a pair of tapped holes 3l which receive fillister head screws 32 that are passed through four holes in a circular plate 33 disposed within the turntable 25. The plate 33 is preferably made of laminated phenolic sheet and is seated on an internal annular shoulder 34 formed on the inside of the turntable. The adjoining end surfaces of the turntable 25 and housing 21 are provided with cylindrical grooves to receive an O-ring 35 of neoprene or other rubber-like material which provides a frictional medium between the two members. When the screws 32 are tightened up. the housing 21 is- `clamped to the turntable 25 with sufficient resistance against turning, bv virtue of the O-ring However. if it is desired to turn the elbow so as to give a different plane of movement for the forearm. the housing 21 can be turned in the turntable 25 by either pressing the end of the forearm against a stationary object, or twisting the housing with the other hand.
Ihe opposite sides of the housing 21 are pro-f .vided with parallel, at surfaces 4!! which are apertnred at 4I to receive shouldered bearing members 4?.. Extending through the housing 21 and journalled in the bearing members 42 is a shaft 43 having a central bore to receive a bolt 44. The head of the bolt 44 and the nut 45 threaded onto the other end thereof are seated in counterbored recesses formed in the outside surfaces of plugs 45 and 41 which are disposed vin opposite ends of the shaft 43, said plugs being provided with serrated radial flanges B which are seated in comoanionately serrated holes 5l in side arm portions 52 of a saddle 53.
`The saddle 53 has a semi-cylindrical body 54 with downwardly projecting arm portions 55 on opposite sides thereof, said body and arm portions being disposed on the inside of the forearm shell Il and bonded thereto by the plastic material when the shell is formed on the cast and cured in the oven. Holes 56 are provided in the body and arm portions of the saddle to obtain a good bond between the saddle and the forearm shell.
The plugs 45, 41 are each provided with inwardly directed, tapered hubs 60 which .are
seated within tapered end portions 6I in thecentral bore of the shaft 43. The tapered hubs of the plugs 56, 51 provide a frictional cone clutch connection between the saddle 53 and the shaft 143 so that when the latter is locked to the upper ring gear 63 which is pressed into place.
mechanism or injury to the wearer.
Formed integrally with the left hand half 28 of the housing 21 and projecting inwardly therefrom is a cylindrical hub 62, the inner end of which terminates just short of the center of the housing and is shouldered to receive an external The shaft 43 has a radial flange 64 provided thereon which is disposed closely adjacent the end of the cylindrical projection B2, and pressed onto the periphery of the flange is an external ring gear 85. The ring gears 53 and 65 are substantially identical in shape and size, having the same pitch diameter and the same number of teeth. Meshing with the gears 63, 65 and slidable axially with respect thereto is an internal ring gear 66, the width of which is equal to the comlbinecl width of gears 63, 65. Ring gear 66 is pressed into an annular recess 61 in the flange portion 18 of a cup-shaped housing 1l. The bottom ofthe housing 1I is drilled centrally to form a hole 12, and pressed into this hole is a shouldered bushing 13 which is journalled on and slidable axially with respect to the shaft 43. The housing 1l and associated ring gear 66 are urged toward the right to the position shown in Figure 3 by a conic spiral spring 14 which seats at one end against the inside surface of the left hand housing half 28, and at the other end against the side of the ring gear 65.
The two external ring gears 63 and 65, and the internal ring gear E5 cooperate to function as splined or dog-toothed locking members having a large number of closely spaced splines or teeth, so that the forearm is enabled to be locked with respect to the upper arm in any one of a large number of closely spaced angular positions instead of the three or four positions which have heretofore been provided. The shaft 43, which is connected to the forearm, is adapted to be locked to the housing 21 on the upper arm by moving the internal gear 68 so that its teeth mesh with the teeth of both of the gears 63, 65, as
shown in Figure 3. In this position, the rotatable gear 65 is locked to the stationary gear 63. The device is unlocked by moving the internal ring gear 58 axially with the housing 1l to the Yposition shown in Figure 4, wherein the ring gear from the right hand side of the housing 1I which is engaged by an oppositely extending annular flange S8 provided on a cam member 8l. The flanges 'i6 and 8G are formed with mating sawtoothed cam portions 82 and 83 which cooperate vso that when the member 8| is rotated with respect to housing 1i, the latter is cammed to the left against the pressure of the spring 14. The crests of the cam teeth 83 are cut off fiat to form plateaus 84 upon which the relatively pointed crests of cam teeth 82 bear when the device is in the unlocked condition shown in Figure 4.
The cam member 8| has a central aperture 85 through which the shaft 43 is passed, and is operating lever @2.
@5 to lock the elbow, as in Figure 3.
provided with a radial fiange 86 which is seated for free rotation within an annular recess 90 formed in a ring Si. An operating lever I92 projects outwardly from one side of the ring di and extends through a slot 89 in the housing section 29. The ring member 9| has a serrated or toothed inner surface 93 that is adapted to beengaged by the free end of a pawl 94 pivoted on a pin 95 which is secured in the cam member 8i. The pawl 94 is disposed between the radial ange B and another flange 95 on the member Si, which abuts against the inside surface f the flat portion 40 of the right hand housing section 2S, the free end of the pawl being urged downwardly into 'engagement with the toothed surface 93, by a U-shaped leaf spring S (Figure One end of the spring 9'! is engaged in a notch 93 in the pawl, and the other end bears against the hub of the cam member Si. The pawl 96 engages the teeth 93 and causes the ring member 9! to drive the cam member Si when turned in a counterclockwise direction. Clockwise rotation of the ring member 8i, however, causes the pawl to ratchet freely over the serrations or teeth 93 without transmitting any driving force to the cam memberSI. Thus, it will be seen that counterolookwise rotation of the ring member SI with respect to the housing Il has the effect of cainming the locking device to the unlocked position shown in Figure 4. K
The ring member 9i is adapted to be rocker through a limited angular distance by means of 'a wire or cord IBB having a fit-ting ll attached to its end which is connected by a pin 162 to the The cord l iii; passes upwardly along the stump socket l!! through a guide loop 9c on the latter and is attached at its upper end by a strap it to the front of the harness Vshoulder member Id adjacent the collar bone of the wearer. A downward, forward shrug of the left shoulder (in the case of a left arm amputation, as shown) causes the distance between the upper and lower points of attachment of the strap ft* to lengthen, and produces a pull on the cord Ii which causes the ring member 9i to be rocked upwardly in a counterolockwise direction through sufficient angular distance to raise the cam teeth S2 to the dat tops 84 of cam teeth 33.
When the pull on the cord i0@ is relaxed, the ring member 9! is returned to its original posin tion by a coiled torsion spring M33 which surrounds the iianges 8E and is anchored at one end mi! to the housing 2l and secured at the other end 335 in a hole drilled intol the ring member SI. The spring 2&3 exert-s a clockwise rotational pull on the member di which tends to rotate the latter until stopped by engagement of the lever arm 92 with the bottom end of the slot 5S in the housing 2l.
To release the locking device, the shoulder `is given another shrug, which pulls upwardly on the cord mi), rocking the cani member Si sufciently to move the cam teeth 82 past the ends of the flat plateaus 8G' in cam teeth 83. The housing member l! is then pushed to the right by spring hi, and the cam teeth S2 drop down into full contact with cam teeth 83, shifting the ring gear S back into engagement with both gears When the cord itil is released after this second shrug, the ring member 53! is again returned by spring 163 to its original position, with the lever 92 in the bottom of the slot 89.
The forearm is adapted to be raised `with respect to the upper arm by means of an elbow lift Vto raise tothe desired position.
control cord HU, .one end of which is connected by a strap i Il to the backside of the harness shoulder member M at the lower outside corner thereof, and the other end of which is passed through a hole in a lift lever H2 fixed to and projecting forwardly from the forearm shell I l a short distance below the elbow. The end of the cord liti is knotted on the other side of the lever arm l i2, and the cord is of such length that when the arm is hanging freely at the side of the wearer, the forearm is straightened out. To raise the forearm, the stump socket Hi is swung forwardly, which has the effectof increasing the length between the points of attachment at the ends of the cord i l ii. The resulting pull on the cord Hi), 'acting on the lever arm [l2A causes the forearm lf the elbow joint is locked, it is necessary, of course,`to unlock the same'before the forearm can be raised, and this is done by shrugging the shoulder downwardly and forwardly, as described earlier. A second shrug of the shoulderl causes the elbow joint to lock again.
rfhe forearm shell il is prevented from swinging rearwardly past its extended position by means of a radially extending-limit stop lug H3 which is formed integrally with the shaft i3 adjacent the left hand end thereof. The lug H3 engages one end of a shoulder or boss lid formed lon the inside surface of the cylindrical projection E2 when the arm is straightended out, and
prevents further rearward movement of the fore-y arm.
Control of the hook 9 is obtained by means of a Bowden cable comprising a. stainless steel ilexible conduit M5 which is secured at one end to the forearm shell i l by an anchor connection l i6, and at the other end to theharness shoulder portion It on the back side thereof by another anchor connection IIT. A wire HS extends through the conduit H5 and is slidable therein, one end of the wire being fastened to the operating lever H9 of the hook, and the other end an operating button against the side of his body or against some other object, which is sometimes difficult or inconvenient to do when the arm is raised in certain positions.
Another advantage of the invention is that the large number of teeth on the gears vt3, 65, 66 permit the elbow to be locked in a large number of angular positions instead of the three or four provided for in prior devices.
Still a further advantage of the invention is that the'swivel connection between the housing 2'! and turntable 25 permits the elbow joint to be turned with respect to the stump socket I0 so as to give any desired plane of movement for the forearm shell Il.
While we have shown and described in con'- .siderable detail what we consider to be the preferred form of our invention, it is to be under- 'c1aims appended hereto.
1. In an artificial arm having a stump socket and a forearm shel, an elbow joint comprising a housing fixed to said stump socket, a shaft fixed to said forearm shell and journalled in said housing, a member fixedly mounted on said housing concentric with the axis of said shaft and having a plurality of angularly spaced teeth projecting therefrom, another member fixed to said shaft coaxial with and adjacent to said first-named member and having a plurality of angularly spaced teeth projecting therefrom, a locking element movable axially between a locked position in engagement with the teeth of both of said members and an unlocked position in engagement with the teeth of only one of said members, a plurality of angularly spaced, equidistant cam teeth projecting axially from said locking element in a circle concentric with the axis of said shaft, a rotatable cam member coaxial with said shaft and having a companicnate circle of axially projecting cam teeth engageable with the cam teeth on said locking element to move the latter alternately from one to the other of said locked and unlocked positions when the cam member is rotated a predetermined angular distance in one direction, and means for rotating said cam member through said predetermined angular distance.
2. In an artificial arm having a stump socket and a forearm shell, an elbow joint comprising a housing fixed to said stump socket, a shaft fixed to said forearm shell and journalled in said housing, a member fixedly mounted on said housing concentric with the axis of said shaft and having a plurality of angularly spaced teeth projecting therefrom, another member fixed to said shaft coaxial with and adjacent to said first-named member and having a plurality of .angularly spaced teeth projecting therefrom, a
locking element movable axially between a locked position in engagement with the teeth of both of said members and an unlocked position in engagement with the teeth of only one of said members, a spring urging said locking element toward said locked position, an annular flange projecting axia ly from said locking element and having saw-toothed cam portions, a rotatable cam member arranged coaxial with said locking element and having an annular flange provided vwith cam portions cooperating with said firstnamed cam portions to shift said locking element from said locked position to said unlocked position against the pressure of said spring, the crests of said second-named cam portions being cut off to form plateaus upon which the crests of said first-named cam portions are adapted to bear to hold said locking element in said unlocked position, and means for successively rotating said cam member through limited angular distances whereby said locking element may be cammed over to said unlocked position or, alternatively, released so that said spring is enabled -to return the locking element to said locked position.
3. InV an artificial arm having a stump socket and aforearm shell, an elbow joint comprising having a plurality of angularly spaced teeth projecting therefrom, another member fixed to said shaft coaxial with and adjacent to said firstnamed'member and having a plurality of angularly spaced teeth projecting therefrom, a locking element'movable axially between a locked position in engagement with the teeth of both of said members, and an unlocked position in engagement with the teeth of only one of said members, a spring urging said locking element toward said locked position, cam portions projecting axially from said locking element, a rotatable cam member arranged coaxially with said locking element and having cam portions cooperating with said first-named cam portions to shift said locking element from said locked position to said unlocked position against the pressure of said spring, an operating lever rotatable with respect to said cam member, means providing a driving connection between said operating lever and said cam member in one direction of rotation, a harness adapted to be secured on the shoulders of the wearer, and a cord connecting said operating lever to said harness whereby said cam member can be rotated through limited angular distances by successive shrugs of the shoulder to move said locking element alternately between locked and unocked positions.
4. In an artificial arm having a stump socket and a forearm shell, an elbow joint comprising a, housing fixed to said stump socket, a shaft journalled in said housing, positive locking means for locking said shaft to said housing in any one of several angularly spaced positions, and frictional clutch means connecting said shaft to said forearm shell, whereby said elbow joint is permitted to slip when over-loaded so as to protect said positive locking means against damage and prevent injury to the wearer.
5. In an artificial arm having a stump socket and a forearm shell, an elbow joint comprising a housing fixed to said stump socket, a tubular shaft journalled in said housing, positive locking means for locking said shaft to said housing in any one of several angularlv spaced positions, a saddle fixedly mounted on said forearm shell, a pair of opposed plugs secured to said saddle at opposite sides thereof, said plugs having tapered hub portions which are received within correspondingly tapered socket end portions in said shaft, a bolt passing through the center of said shaft and engaging said plugs to draw them tightly into their respective sockets, said plugs providing a frictional cone clutch connection between said shaft and said saddle whereby the elbow joint is permitted to slip when overloaded so as to protect said positive locking means against damage and prevent injury to the wearer.
6. In an artificial arm having a stump socket and a forearm shell, an elbow joint comprising a housing xed to said stump socket, a shaft fixed to said forearm shell and journalled in said housing, a member fixedly mounted on said housing concentric with the axis of said shaft and having .a plurality of angularly spaced teeth projecting therefrom, another member fixed to said shaft coaxial with and adjacent to said firstnamed member and having a plurality of angularly spaced teeth projecting therefrom, a locking element movable axially between a locked position in engagement with the teeth of both of said members and an unlocked position in engagement with the teeth of only one of said members, a spring urging said locking element toward said locked position, a plurality of angularly spaced, equidistant cam teeth projecting axially from said locking element in a circle concentric/with the axis of said shaft, a rotatable cam member coaxial with said shaft and having 9 10 a companlonate circle of cam teeth engageable UNITED STATES PATENTS with said first-named cam teeth, said cam mem- Number Name Date ber being operable to move said locking element 1,334,834 Blatchford Man 23I 1920 from said locked position to said unlocked posi- 1,507,632 y pecorella et al Sept. 9, 1924 tion against the pressure of said spring, and 5 1151071993 Hoare et a1 Sept-1 9, 1924 means for successively rotating said cam member through limitedA angular distances whereby FOREIGN PATENTS said locking element may be cammed over tof YNumber Country Date said unlocked position or, alternatively, released 4113,207 Great Britain Feb. 14, 1918 so that said spring is enabled to return the lockl0 127,599 Great Britain Nov. 27, 1919 ing element to said locked position. 116,530 Great Britain Mar. 13, 1922 MEYER FISHBEIN. 187,065 Great Britain Oct. 19, 1922 MICHAEL J. NAGY. `392,614 Germany Dec. 20, 1917 DONALD M. THREEWIT. @36,757 Great Britain Oct. 23, 1930 15 $485,583 France Jan. 19, 1916 REFERENCES CITED 9573.613 Great Britain Nov. 28, 1945 The following references are of record in the file of this patent: