US3403675A - Universal dynamic traction carriage - Google Patents

Description

Oct. 1, 1968 J. w. CARR 3,403,675

UNIVERSAL DYNAMIC TRACTION CARRIAGE Filed Nov. 16, 1964 M 5 Sheets-Sheet, 1

L/OHN 14/. CAez INVENTOR.

I I I g ll .1" 35 mm Mi Oct. 1, 1968 J. w. CARR 3,403,675

UNIVERSAL DYNAMIC TRACTION CARRIAGE Filed NOV. 16, 1964 5 Sheets-Sheet 2 i 25 /20 [Ma L/OHN W CA 22 INVENTOR United States Patent 3,403,675 UNIVERSAL DYNAMIC TRACTION CARRIAGE John W. Carr, 168 Cronin Drive, Santa Clara, Calif. 95051 Filed Nov. 16, 1964, Ser. No. 411,644 13 Claims. (Cl. 128-75) ABSTRACT OF THE DISCLOSURE A compound low inertia, low friction carriage; calibrated spring traction device mounted to the frame of a wheeled sub-carriage which tracks along an elastically controlled vertically deflectable monorail; all components and component functions cooperate to meet the dynamic requirements of an active seated or bedded patient. When the carriage is operatively mounted with respect to a chair the patient may carry out the usual tasks of a normal seated worker and thereby be productive while in traction.

This invention is a versatile mechanism adapted for the general application of traction to the human patient in a seated position or in bed.

Most devices presently in use do not allow for freedom of movement of the parts of the patients body under traction, or if such movement is possible, it is usually accompanied by acceleration or deceleration forces reacting on the patient. Even with movable weight traction systems the point, relative to the part of the body under traction, from which traction forces are applied, is usually fixed. This puts rather severe restraints on movements of the portion of the body under traction.

Wherefore, it is the primary objective of this invention to introduce a universal'dynamic traction carriage which will not only result in increased comfort to bed patients subject to traction, but will also, for cervical and lower back and pelvic traction, allow a patient to comfortably remain at seated work or at other normally seated activities while having therapeutic traction applied. The application of the carriage for a seated patient is primarily for cervical or lower back and pelvic traction. A system of applying lower back and pelvic traction to a person engaged in seated activities, including a special suspension belt developed particularly for the application of lumbosacral traction to a seated patient has been introduced elsewhere by this inventor. See Ser. No. 92,100 filed Feb. 27, 1961, now US. Patent No. 3,167,068.

A use of that belt with the present universal traction carriage will be referred to in the following description. The present invention is concerned not with the traction application means to the part of the body under traction, but rather with the freedom of movement in up to three dimensions of the point in space from which the applied traction forces are produced. In addition to this spatial dimensional freedom, use is also made of the application of Hookes law (as introduced in the above reference by this inventor) to the time domain freedom of acceleration and deceleration forces by the use of elastic low inertia members.

It is recognized by the inventor that various specific combinations of the principles herein introduced with those introduced in the above reference (US. Patent No. 3,167,068) could result in variously different structures in detail, but would be only a state of the art variation of application of the principles thus disclosed.

In a typical cervical traction embodiment of the invention the patient is provided with one of the existing cervical head sling apparatus and is seated in a chair. To the back of the chair is attached a vertically directed linear structural member, the upper end of which extends six to seven feet above the floor on which the chair is stand- "ice ing. Near the upper end of this member is attached a hinge or swivel and to the movable side of the hinge is attached, in cantilever, another linear structural member which, under no load, lies in essentially a horizontal plane and is most conveniently in the form of a metal tube or rod, the outside curvature of which serves as the track for a circumferentially grooved pulley or wheel which is mounted in a U-shaped block. To the bottom of the block it attached a calibrated spring or springs which are the source of the traction reactive forces. The wheel tracks radially with respect to the hinge joint on the upper side of the cantilevered monorail member. The length and cross section modulus of this hinged cantilever track, which is in this case part of the primary carriage, are chosen so that the vertical downward deflection of the point of application of a load, equal to the prescribed traction forces, on the radially moving wheel (of the subcarriage) is approximately the amount that a patients chin will vary in elevation as he moves his head from the position it has in a normal upright seated position to a normally required forward and downward position as in bending over a desk to write. Starting with the primary carriage a one dimensional freedom of motion from side to side is provided. In this particular example this is an angular motion. (Another method of providing the primary carriage motion could be, for example, a two wheel carriage on a laterally oriented rigid track.) The second dimension of mechanical freedom of motion is provided by the sub-carriage wheel free to move in a radial direction with respect to the hinge joint. The third dimension of mechanical freedom, resulting in complete three dimensional freedom of motion of the traction loaded axle of the sub-carriage wheel, is accomplished in this particular example, by the deflectible cantilever monorail on which the sub-carriage wheel tracks. When a traction load is applied to the monorail wheel and these traction forces transmitted to a cervical traction sling applied to a patients head, it can readily be seen that the patient has full three dimensional freedom of movement of his head in carrying out normal seated activities. Equipping the subcarriage with a calibrated spring traction, and taking care that the moving parts are of low weight, provides the patient with a low inertia traction in the four dimensional space-time domain of a dynamic system. Weights, depending from the sub-carriage may be used as the traction source. However, now there are inertial forces of acceleration and deceleration including the impulses of starting and stopping, which must be absorbed by the mechanism and the patient.

Specific embodiments of the invention as well as the general versatility of it will be clearly apparent from the following description and accompanying drawings.

FIG. 1 is a perspective view of the specific example generally described above.

FIG. 2 is an expanded scale drawing of half of a symmetrical spring calibrated traction sub-carriage mechanism operatively mounted to the sub-carriage tracking wheel.

FIG. 3 shows an alternative method of providing a vertically defiectable monorail on which the sub-carriage wheel tracks. In addition it shows extended bars and vertically depending straps for lower back and pelvic traction application. It also shows that the mechanism may be supported by a wall or beam bracket rather than being mechanically fastened to the chair.

FIG. 4 shows the application of restricted versions of the device in which only two degrees of mechanical freedom may be required by a bed patient in cervical and/or leg traction.

FIG. 5 shows a bag of weights which may be used in lieu of the calibrated spring traction.

Referring to FIGS. 1 and 2 a torso 10 of a patient is shown seated on a chair 11 at a table 12 with one of a variety of existing cervical traction head slings 13 in operative position. A structural member 14 is attached in a horizontal lateral orientation to both rear chair legs. To the mid-section 16 of structural member 14- is attached the lower region 18 of vertical support member 17. Vertical support member 17 is attached to the chair 11 at central region 19 of the top portion of back 20 by means of a slotted L-section bar 21. The base of the slotted L-section is bolted or clamped to the top portion of back 20 and a bolt passes through vertical member 17 and the slot in bar 21. The slot provides for adjustment to put member 17 in a vertical position. Hinge 22 is firmly attached to the upper region of vertical support 17. To the upper part of the rotatable side of hinge 22 is attached an operationally stiff structural cantilever member 23. To the lower part of the rotatable portion of hinge 2.2 is attached an operationally deflectable resilient cantilever member 24 which, together with the rotatable portion of hinge 22, serves as the primary carriage monorail providing azimuthal freedom of motion. A chain 26 of proper length to limit any possible extreme deflections of operationally deflectable resilient cantilever monorail 24 is attached to the free ends of stiff cantilever member 23 and monorail 24 Wheel 25, tracking radially on monorail 24, and bearing the traction load, provides radial freedom of motion. Clamp 28 can be moved radially on monorail 24 to serve as a rear stop for wheel 25 to thereby adjust the forward angle of traction when the patient is erect. In addition clamp 28 connects to chain 29 which in turn is movably connected to stiff cantilever member 23. Chains 29 and 26 thus provide a safety device in case member 24 should ever break at the point of highest stress 30. Monorail 24, operationally deflectable within its elastic limit under normal traction load, provides the vertical dimensional freedom of motion. In selecting monorail '24- structural analyses of the resultant single point loaded cantilever structure must be made taking due consideration of the amount of vertical deflection required under a given average traction, maximum moment, maximum stress at point 30 of member 24 as a result of this maximum moment, and the total dynamic nature of the operational stresses including fatigue under continued cyclic usage. The same applies for the possible high peak loads on operationally stiff cantilever member 23. Pin 27 serves as a stop for block 31 which is operationally connected to wheel 25 by axle pin 32. Swivel pin 34 connects bars 33 to block 31. Spring support tubes 35 ar inserted into holes in bar 33 and held by set screws 36. From pins 37 in the upper end of support tubes 35 depend extension springs 38, the lower ends of which are mechanically ganged together by gang bar 39 connected to the lower ends of the springs 38 by links 40 through holes 41 in bar 39. Spring housing tubes 43 are attached to bar 39 by pins 44 through holes in the walls of the tubes and through holes 42 in the bar. Light chain 45 is adjustably hooked to the center of gang bar 39 via hook 46. Either spring housing tube 43 is calibrated with numbers 47 to indicate the amount of traction being applied. The lower end of chain 45 is operationally connected to the spreader bar 13a of a conventional cervical traction sling 13.

The fundamental operational nature of the carriage is now quite evident. A patient wearing traction sling 13 seats himself in chair 11. He then reaches up and hooks sling 13 to the ends of spreader bar 13a, chain 45 having been set at the correct linkage to hook 46 to provide the prescribed amount of traction as indicated by numbers 47 on one of the spring housing tubes 43. Clamp 28 has previously been adjusted for the desired angle of traction when the patient is in an erect position. As the patient 10 moves back and forth, wheel 25 tracks on monorail 24 which deflects in increasing increments as wheel 25 moves radially outward from the hinge. The downward deflection for a constant load on the cantilever monorail of constant cross section is proportional to the distance from hinge 22 to the center of wheel 25 raised to the third power. This tends to keep the distance between wheel 25 and spreader bar 1311, on the head sling 13, constant,

thereby resulting in essentially constant spring tension which bears a constant relationship with the traction applied. The angular motion provided by the hinge 22 allows the patient 10 to move his head from side to side, likewise without increasing or decreasing spring tension. Swivel pin 34 allows patient 10 the freedom of twisting his torso or head without encountering any resistive forces. Good design seeks to keep the weight of all members loading wheel 25 at a low value to make the effect of their mass inertial actions on the patient small, and thereby take maximum advantage of the spring applied tension principle.

Referring to FIG. 3 hinge 111 is attached to partition clamp 112 so that the traction system may be supported along the top edge of a partition wall. Hinge 111 could as well be attached directly to a flat wall surface. The assembled mechanism shown supported by wheel 25 is in every detail identical to that fully described previously in the description relative to FIGS. 1 and 2. The method of obtaining the primary carriage motion in this example is the same as that in FIG. 1. To hinge 111 is attached radial operationally rigid cantilever member 114 having vertical projection 114a at its free end to support extension spring 115. The monorail 113 on Which wheel 25 tracks, is rotatably mounted in a vertical plane to hinge 111 by means of a rotating joint 116. The other end of monorail 113 which is operationally essentially stiff in this application is supported by extension spring 115. Chain 117 prohibits extreme deflections and/or possible breakage of spring 115. Pin 118 and clamp 119 serve the same functions as pin 27 and clamp 28 of FIG. 1. In this example as the sub-carriage wheel 25 moves radially outward under load the end of monorail 113 supported by spring moves downward increasingly as wheel 25 moves radially outward from hinge 111. In this example, if spring 115 is linear and manufactured without any initial tension, the amount of vertical deflection under constant load on wheel 25 will be directly proportional to the distance between hinge 111 and the center of wheel 25. However, if the spring is linear and fabricated with initial tension then a given load on wheel 25 will have to be moved radially far enough out from the hinge 111 to overcome the initial tension before downward vertical deflection takes place. The spring constant of spring 115 and the amount of initial tension in spring 115 can both be designed to give the approximate required deflection for operation. By using stiffer springs (38 in FIG. 2) and a stronger extended bar 120 (39 in FIGS. 1 and 2), and strong spring 115, stronger stiff cantilever member 114, and stronger monorail 113, the carriage can be adapted for lower back and pelvic traction. Straps 121, adjustable in length by friction buckles 122, are fastened to bar 120 by being threaded through slots 123 and have hooks 124 depending from their lower ends. The hooks 124 are detachably connectable to a suspension belt worn about a patients lower thoracic region. The belt is equipped with traction engagement rings located directly under the patients armpits. This belt has been disclosed in Ser. No. 92,100, filed Feb. 27, 1961, now U.S. Patent No. 3,167,- 068.

Other types and uses of elastic members can be used to obtain similar actions to those discussed. For example, it will be noted that the main vertical structural member 17 to which the hinge 22 in FIG. 1 is attached could also be chosen to be increasingly defiectable under an increasing load moment and thereby provide a portion of the necessary deflection of the applied load point on the subcarriage, the hinge itself would move forward as the patient moved forward and downward. Also the monorail could be a rigid member supported by a compression or torsion spring or torsion bar at the hinge. Also, for example, a multiturn torsion spring housed and mounted to the sub-carriage wheel could be used to obtain the traction in lieu of the extension springs 38, spring housing tubes 43, and spring support tubes 35 of FIGS. 1 and 2.

Refer now to FIG. 4 where simplified versions of parts of the basic carriage may be used to apply, for example, cervical and/or leg traction to a patient in bed. Only two dimensional mechanical freedom of motion, maintaining constant traction, is shown here, but the more complicated three dimensional freedom carriage can be used for these applications if desirable.

In FIG. 4 patient 200 is supported in a semi-seated position in bed 201 by elevated section 202. Bed 201 is equipped with a rectangular frame 203 of conventional type. Refer first to the cervical traction device. Carriage support 204 is fastened to frame 203 by clamp 205. Hinge 206 is attached to the lower portion of carriage support 204. To the rotatable portion of hinge 206 is attached, in cantilever, operationally rigid linear structural members 207 and 208. These two members rigidly fastened to each other at the free ends by spacer 209 and bolt 210 form a rigid box-like complex cantilever beam which, with the hinge, constitutes the primary carriage providing azimuthal freedom of motion with respect to support 204. Lower member 208 of this structure is most conveniently fabricated from right circular cylindrical tubing or rod to best serve as a rail. Wheel 209a mounted in block 210a constitutes the secondary carriage, providing radial motion with respect to hinge 206 and support 204. On block 210a is attached an extension spring 212 and a thin strip of metal 211 on which spring traction calibration marks 213 are placed. Chain 215 adjustably linked to hook 214 on the lower end of spring 212 provides adjustable traction applied to cervical traction head sling 216 operationally attached to patient 200.

Refer now to the leg traction in FIG. 4. Carriage support 250 is rigidly fastened to frame 203 by clamp 251. Support 250 has several sets of holes in the lower portion drilled in paired matched alignment with the holes in the stationary portion of hinge 252 so as to allow for vertical adjustment of hinge 252. To the moving portion of hinge 252 operationally rigid linear structure members 253 and 254 are attached in cantilever and rigidly fastened together by spacer 255 and bolt 256. Together with the moving part of hinge 252 this structure provides for azimuthal rotation and constitutes the primary carriage. Member 253 is extended to provide a radially long arm. On 253 is mounted extension spring 257 which is attached at one end, 258, to member 253, and at the other end 259 to rope 260. Spring calibration marks 257a indicate the amount of traction applied. Rope 260 extends over pulley 261 which rotates on shaft 262 attached to the extended end of member 253. The other end of rope 260 is adjustably link connected to foot sling 264 operationally attached to patient 200. Wheel 265 in block 266 constitutes the sub-carriage means which gives radial freedom of motion with respect to carriage support 250 and hinge 252. D ring 267 is connected to block 266. Web strap 268, adjustable in length by friction buckle 269 threads through D ring 267 at the pulley block and hook 270 at the lower end, which is detachably connectable to knee support sling 271.

Thus it is depicted how two two-dimensional carriages can be adapted to apply cervical and leg traction simultaneously to a patient in a bed, with the patient retaining maaility of head and shoulders and of the leg under traction. Of course the two types of traction can be used separately for leg or cervical traction, or for applying traction to other parts of the body.

Referring to FIG. 5 bagged weights 300 are connected to rope 302 by coupling 301. Extended member 305 is member 253 in FIG. 4. Pulley 303 is rotatably attached to 305 by shaft 304. Rope 302 passes over pulley 303 and is coupled to foot sling 306 which is operationally attached to a patient.

It is obvious that weights may be used with any of the traction types shown in lieu of the springs.

Placement of the operationally rigid structurally stiff cantilever member in FIG. 1 and FIG. 3 could be to either side of or below the defiectable monorail. Various other means of limiting the defiectable member could be used.

The defiectable monorail 24 in FIG. 1 and 113 of FIG. 3 could be held in a deflected position and fastened rigidly at both ends to the stiff cantilever member or it could be a permanently formed rigid structure having one or more formed rails.

For such applications as may require the patient to be standing the carriage mechanism shown in FIG. 1 and FIG. 3 may be supported by any convenient supporting structure such as a wall, ceiling, or table, the chair not being necessary. For instance this may be used by a draftsman standing up at a drafting board, in which case a primary and sub-carriage means each tracking respectively along the X-Y coordinates of a cartesian coordinate system, with two ends of the primary carriage support fastened to the ends of a drafting table or board, could conveniently be used.

The attachment of the vertical support to the rear of the chair as shown in FIG. 1 is convenient, but the vertical support could as well be composed of two or more members attached, for instance, to the sides of the chair or other seating means.

I claim as my invention:

1. A passive mechanism, for applying cervical, lower back, or leg traction to a patient, comprising a primary carriage operatively connectable to a carriage support means above a bed or a chair, a track connected to and supported by said primary carriage, a wheeled subcarriage operatively connected to and constrained to move along said track, traction means operatively connected to said sub-carriage, tension transmitting means operatively connected to said traction means and operatively connectable to a traction application means on a patient.

2. A passive mechanism, for applying cervical or lower back and pelvic traction to a seated patient, comprising a vertical support member operatively connected to a chair, primary carriage and carriage support means operatively connected by means of a hinge to said vertical support member, a track connected to and supported by said primary carriage, a wheeled sub-carriage operatively connected to and constrained to move along said track, calibrated spring traction means operatively connected to said sub-carriage, tension transmitting means operatively connected to said traction means and operatively connectable to a cervical or lower back traction application means on a seated patient, all constituent parts and part functions cooperating with said traction application means on said patient to permit said patient to make normal seated body and limb movements to perform the normal work functions of a normal seated person while he is under essentially constant traction.

3. A passive mechanism, for applying traction to a patient, operatively connectable to a mechanism support means, comprising primary carriage means free to move along one coordinate in an essentially horizontal plane, a monorail track operatively connected to said primary carriage means with its no load orientation extending in essentially a horizontal plane at essentially right angles to the line of motion of said primary carriage means, said monorail track operatively defiectable under load in a vertical plane in a manner providing elastically controlled increasing downward vertical deflection of a point on said monorail where said load is applied as the distance from said point to one end of said monorail increases, wheeled subcarriage operatively connected to said operatively defiectable monorail and constrained to track along a portion of the length thereof, traction means operatively connected to said sub-carriage means and operatively connectable to a traction application means on a patient when a patient is operatively positioned with respect to said carriage means.

4. A passive mechanism, for applying lower back or cervical traction to a seated patient, comprising a chair, vertical support means operatively connected to said chair, a horizontal primary carriage operatively connected to said vertical support means and free to move from right to left with respect to said chair, a track operatively connected to said primary carriage with its no load orientation in a horizontal plane at right angles to the line of motion of said primary carriage, said track operatively deflectable under load in a vertical plane in a manner providing elastic controlled increasing downward vertical deflection of a point on said track where said load is applied as the distance from said point to one end of said track increases, wheeled sub-carriage operatively connected to said operatively deflectable track and constrained to track along a portion of the length thereof, calibrated spring traction means operatively connected to said subcarriage and operatively connectable to a cervical or lower back traction application m ans on a seated patient.

5. A passive mechanism, for applying traction to a patient, comprising hinge means, means for operatively connecting one leaf of said hinge means to a supporting structure, an operationally rigid horizontally oriented linear structural member in cantilever attachment to the rotatable leaf of said hinge, an operationally deflectable monorail, first end of said operationally deflectable monorail operatively connected to the rotating portion of said hinge, second end of said monorail operatively connected to the free end of said operationally rigid cantilever member in a manner allowing a limited elastically controlled downward motion of said operatively deflectable monorail, a wheel which tracks on said monorail, a traction support means operatively attached to the axis of said wheel, calibrated spring traction means operatively at tached to said traction support means, tension transmitting means operatively attached to said traction means and operatively attachable to a traction application means when said traction application means is operatively attached to a patient when said patient is operatively positioned with respect to said mechanism.

6. A passive mechanism for applying cervical or lower back traction to a seated patient in accordance with the provisions of claim 2 wherein said track is a monorail consisting of an operationally deflectable resilient linear member cantilever mounted to said primary carriage means.

7. A passive mechanism for applying cervical or lower traction to a seated patient in accordance with the provisions of claim 2 wherein said track is operationally essentially rigid, first end of said track connected to said primary carriage means by a pivotal rotating joint, second end of said track operationally suspended from said primary carriage by a spring.

8. A passive mechanism in accordance with claim 2 wherein said track, is an operationally essentially rigid structural member, with the edge or surface which serves as the tracking surface formed in increasing downward slope in the vertical plane in the direction in which a patients trunk would make a forward bending motion when a patient is using said mechanism.

9. A passive mechanism for applying cervical and or leg traction to a patient in a :bed equipped with tractionsupport frame, comprising a primary carriage to provide first coordinate motion in a horizontal plane operatively connected to said traction support frame, a wheeled subcarriage running along a track mounted on said primary carriage to provide motion along a second coordinate in a horizontal plane essentially at right angles to said first coordinate, traction means operatively attached to said sub-carriage, tension transmitting means operatively connected to said traction means and operatively connectable to a traction application means on a patient such that when a patient is setting upright in said bed he may move his head and trunk and leg, that are in traction, back and forth or sideways under essentially constant traction,

10. A passive mechanism for applying traction to a patient, comprising operational mechanism support means, primary carriage means operatively connected to said mechanism support means and free to move from right to left or forward and backward, structural member operatively connected to said primary carriage means, said structural member formed in a vertical plane in a manner providing a rail with increasing downward slope, subca rriage means operatively connected to said structural member and constrained to track along a portion of said rail, traction means operatively connected to said subcarriage means and operatively connectable to a traction application means on a patient when said patient is operatively positioned with respect to said carriage means.

11. A passive mechanism for applying traction to a seated patient, comprising a chair, a vertical support member operatively connected to said chair and extending thence upward, a hinge operatively connected to the upper portion of said vertical support member, an operationally rigid horizontally oriented linear structural member in cantilever attachment to the rotatable side of said hinge, an operationally deflectable linear structural member capable of serving as a monorail for a wheel, one end of said operationally deflectable monorail member operatively connected to the rotating portion of said hinge, said monorail operatively connected to said operationally rigid cantilever in a manner allowing a limited elastically controlled downward motion of said operatively deflectable monorail, a wheel which tracks on said monorail, a traction support means operatively attached to the axis of said wheel, calibrated spring traction means operatively attached to said traction support means, tension transmitting means operatively attached to said spring traction means and operatively attachable to traction application means when said traction application means is operatively attached to a patient when a patient is seated on said chair.

12. A passive mechanism for applying traction to a seated patient, comprising support means operatively connectable to a chair, said support means having a vertical member extending above the back of said chair when operatively connected thereto, a hinge operatively connected to the upper portion of said vertical support member, an operationally rigid horizontally oriented linear structural member in cantilever attachment to the rotatable leaf of said hinge, an operationally deflectable monorail, first end of said operationally deflectable monorail operatively connected to the rotating leaf of said hinge, second end of said monorail operatively connected to the free end of said operationally rigid cantilever imember allowing a limited elastically controlled downward motion of said operatively deflectable monorail, a wheel which tracks on said monorail, a traction support means operatively attached to the axis of said wheel, calibrated spring traction means operatively attached to said traction support means, tension transmitting means operatively attached to said spring traction means and operatively attachable to a traction application means when said traction application means is operatively attached to a patient when a patient is seated on said chair.

13. A passive mechanism for applying cervical traction to a seated patient, comprising calibrated spring traction means operatively adjustably connectable to a traction application means on a patient; said traction means operatively connected to the frame of a subcarriage means; a wheel and axle operatively mounted to said frame of said sub-carriage means; a primary carriage comprising an operationally stiff elastic cantilever member and an operationally elastically deflectable cantilever monorail oper atively connected to a common cantilever support base and said base operatively connected to a rotatable first leaf of a hinge; the free end of said cantilever monorail connected to the free end of said stiff cantilever member by means of a first flexible tension transmitting member,

said first flexible tension transmitting member serving as a deflection limiter to the free end of said monorail along which said sub-carriage means moves on said wheel and axle; a second flexible tension transmitting means the tWo ends of which are adjustably translationally connected respectively to said operationally stiff cantilever member and to said monorail between said sub-carriage and said hinge, said adjustable connections of said ends of said second flexible tension transmitting means serving as a safety device against possible breakage of said cantilever monorail and as a rear position limit of said sub-carriage; the second leaf of said hinge operatively connected to a vertical support member; said vertical support member operatively connected to a patient seating means; said patient seating means, said vertical support member, said primary carriage and sub-carriage, said calibrated spring traction means all operating in coordination with said traction application means on a seated patient so that said seated patient may carry out normal seated activities under essentially constant low inertia traction.

References Cited UNITED STATES PATENTS 821,116 5/ 1906 Nunamaker 297-275 935,170 9/1909 Smith 581 1,269,734 6 1918 Noland 584 1,731,709 10/ 1929 Cropsey 592 2,166,229 7/ 1939 Anderson l2887.2 2,714,885 8/1955 Uhland 128--75 2,772,675 12/1956 Simmons 12887.2 2,843,114 7/1958 Hall 128-75 2,929,375 3/1960 Spinks l28 84 2,938,695 5/ 1960 Oiampa 128-75 3,060,929 10/ 1962 Zivi 128-75 3,105,489 10/1963 Zivi 128-75 FOREIGN PATENTS 726,666 3/ 1932 France. 830,264 5/ 1938 France.

L. W. TRAPP, Primary Examiner.

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