GB2177308A

GB2177308A - A traction device

Info

Publication number: GB2177308A
Application number: GB08616046A
Authority: GB
Inventors: Victor Jan Rogers
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-07-02
Filing date: 1986-07-01
Publication date: 1987-01-21
Also published as: GB8616046D0; GB8516738D0

Abstract

A traction device (1) for medical or exercising use comprises turnable reel (8), spring (13) providing a spring force urging the reel in a first rotary direction into a first position, and a flexible, substantially inextensible elongate member (15) wound at least partly around the periphery of the reel when the latter is in its first position and having one end attached to the periphery of the reel and its other end arranged so that it can be pulled to turn the reel out of its first position, in opposition to the spring force, in a second rotary direction to unwind the elongate member. The traction device (1) further comprises adjustment means (21-24) for enabling pre-adjustment of the spring force exerted by the spring (13). The arrangement may provide constant traction force, irrespective of the amount of member (15) which is unwound. <IMAGE>

Description

SPECIFICATION A traction device This invention relates to a traction device and in particular, but not exclusively, to a medical traction device for traction of a patient's bones and/or skin.

According to the invention a traction device comprises support means, reel means turnably supported by said support means, spring means providing a spring force for urging the reel means, in a first rotary direction, into a first position, a flexible, substantially inextensible elongate member extending around at least part of the periphery of the reel means when the latter is in its first position and having one of its ends attached to, e.g. to the periphery of, the reel means and the other of its ends arranged so that it can be pulled to turn the reel means out of its first position, in opposition to said spring force, in a second rotary direction opposite to said first rotary direction thereby to at'least partly unwind the elongate member from the reel means, wherein the traction device further comprises adjustment means for enabling pre-adjustment of the spring force exerted by the spring means.

The traction device is primarily intended to function as an apparatus for exerting a continuous pulling or traction force over a period of time on a skeletal structure (as in a fracture) and, as such, typically operates with the de- vice attached to a fixed structure (e.g. a hospital bed) and the elongate member, in a partially unwound state, attached to a patient for bone and/or skin traction. In such use, the spring force exerted by the spring means provides the traction force, and this traction force is present whenever the elongate member is unwound partially or fully from the reel means so that the latter is turned out of its first position. Although primarily intended for use as a medical traction apparatus, the traction device can be used as an exercising apparatus.In such usage, the flexible elongate member is intended to be repeatedly unwound from, and wound back onto, the reel means.

When the reel means is in its first position, the elongate member may be wound in one or more complete turns around the periphery of the reel means. However, preferably the elongate member is wound through an angle of less than 360" around the periphery of the reel means when the latter is in its first position. In this latter case, the reel means is conveniently in the form of an eccentric wheel arranged so that the distance from the point on the periphery of the wheel at which the elongate member leaves contact with the wheel periphery to the turning axis of the wheel increases as the reel means turns in said second rotary direction.Thus during the application of a pull force to unwind the elongate member from the reel means, the torque exerted by the pull force increases, as the reel means turns in said second rotary direction, to counteract an increase in torque required to turn the reel means occasioned by the spring force exerted by the spring means increasing as it is placed under greater spring tension as the reel means turns in said second rotary direction. By suitable design of the eccentric wheel, the traction force generated by the traction device is substantially constant however much the flexible elongate member is unwound from the reel means.This is particularly desirable for medical traction apparatus, where it is required for bones to be placed under constant traction for long periods of time during which limb movement may occur changing the amount by which the elongate member is wound around the reel means.

Preferably stop means are provided for preventing turning of the reel means in said second rotary direction past a second position.

Typically the reel means is turnable through an angle of less than 360 , e.g. 340" during movement from its first position to its second position or vice versa.

Conveniently the spring means comprises a spirally wound spring, e.g. a coil spring of wound spring strip material, having one of its ends fixed relative to the reel means and the spring adjustment means comprises a rotatable member to which the other end of said spring is fixed which is adjustably turnable relative to the reel means to adjust the angle through which the spring is wound for adjusting said spring force.

Typically the reel means is fixed to an axle turnably mounted in the support means, the spring adjustment means comprises a casing surrounding, and turnable relative to, the axle, and the spring means comprises spring material spirally wound or coiled about the axle within said casing and having one end fixed to the axle and the other end fixed to the casing.

Conveniently, the adjustment means further includes a manually adjustable setting wheel for setting via gearing the position of the casing.

In this case the casing may be provided with a worm wheel meshing with a worm turned by said setting wheel. Stop means are suitably provided for limiting turning of the casing, e.g.

to approximately four revolutions.

Means, e.g. an indicating dial, may be provided for providing an indication representative of the spring force pre-set by the adjustment means.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side sectional view of traction device according to the invention, and Figure 2 is a sectional view taken on the line ll-ll of Figure 1.

Figures 1 and 2 show a medical traction device, generally designated by the reference numeral 1, which includes a main frame in the form of a base 2, on which is mounted spaced apart axle supports 3 and 4 for turnably supporting an axle 7 in bearings 5 and 6, respectively, and an outer casing 50 fixed to the base 2. A wheel 8 is fixed to the axle 7 by means of a pin 9 and a generally cylindrical spring casing 10 housing a coil spring 13 is rotatably mounted on the axle 7 by means of bearings 11 and 12.

The periphery of the wheel 8 is grooved, the bottom of the groove following an eccentric path about the axis of the axle 2 to define an eccentric peripheral surface 14 around which a flexible, inextensible elongate member 15, e.g. in the form of a steel cable, is partly wound. The eccentric peripheral surface 14 follows a generally spiral course from a radially outer end 14a to a radially inner end 14b.

One end of the flexible elongate member 15 is attached to the radially outer end 1 4a and its other end is provided with attachment means in the form of a ring 16. The elongate member 15, from its point of connection to the radially outer end 14a of the peripheral surface 14, is wound about the eccentric or spiral peripheral surface 14 before leaving contact with the latter and passing through a hole 17 in the base 2. The elongate member is guided into the hole 2 from the wheel 8 by being passed partly around the grooved periphery of a guide wheel 18 mounted on the base 2.

The coil spring 13 has its radially inner end fixed to the axle 7 by means, for example, of a screw-threaded member 19 and its radially outer end fixed to the cylindrical wall of the casing 10 and is designed to exert a spring force F, via the axle 7, on the wheel 8 in a first rotary direction R. The spring force F can be adjusted by means of an adjusting mechanism comprising a worm wheel 21 fixed, e.g.

by bolts 22, to the casing 10 and a worm 23 mounted on the base 2 and manually turnable by means of a wheel 24.

Stop means are provided for limiting the number of turns that the casing 10 can be rotated by the adjustment mechanism. Convenient stop means are provided by stops 25 (only one of which is shown in Figure 1) at opposite ends of a helical track 26 on the periphery of the casing 10. The helical track 26 may, for example, be in the form of steel rod or wire helically wound around the casing 10 and received in a grooved member 27 mounted on the base 2 for pivotal movement about a pivot axis 70. As the spring casing 10 is turned by manual rotation of the wheel 24, the grooved member 27 moves along the helical track 26 between the stops 25 at opposite ends thereof.

An indicator wheel 30 is mounted on the base 2 and is drivingly connected to the spring casing 10 by means of an endless belt 31.

The indicator wheel 30 is provided with circumferential markings (not shown) visible through a window (not shown) in the outer casing 50. The diameters D1 and D2 of the portions of the wheel 30 and casing 10, respectively, about which the belt 31 travels are chosen with regard to the angular distance between the two stops 25. If there is an angular distance of 1000" between the two stops 25 (i.e. the casing 10 is turned through 1000" from one to the other stop), then the ratio of D1:D2 should be no greater than 1000:360, typically 2.5:1.

A stud 40 is fixed to the wheel 8 and projects therefrom substantially parallel to the axle 7. The stud 40 is designed to abut against the axle support 3 (or against stop means provided on the axle support 3) to limit angular movement of the wheel 8 to less than 360 , (e.g. 340 ). In order to retain the flexible elongate member seated within the grooved periphery of the wheel 8, a cover 41 is mounted on the axle 7 and has an annular flange 42 closely surrounding the periphery of the wheel 8. The flange 42 has an opening 53 therein to enable the elongate member 15 to pass therethrough and is provided with an arcuate slot 44 around which the stud 40 is moved during movement of the wheel 8. The cover 41 may be fixed, or turnably mounted (as shown) at least to a limited extent, on the axle 7.

In use of the traction device 1, the latter is fixed to a support (not shown), e.g. by connection to a bed frame using an attachment ring 60 fixed to the casing 50. The ring 16, with the flexible elongate member 15 in a wound, retracted rest position, is then pulled with a pull force P in a direction A so as to overcome the counteracting spring force F and turn the wheel 8 out of its limiting rest position in a second direction opposite to the first rotary direction R. With the flexible elongate member 15 partly unwound from the wheel 8, the ring 16 is attached to a patient, e.g. to a pin fixed to a patient's bone or to adhesive strapping wrapped around a patient's limb, so that the partly unwound elongate member 15 exerts traction by virtue of the spring force, on the patient's skeletal structure. Since the distance between the axis of the wheel 8 and the point on the eccentric peripheral surface 14 at which the elongate member 15 leaves contact therewith changes in dependence on the amount that the elongate member 15 is unwound from the peripheral surface 8, the torque applied on the axle 7 through the wheel 8 also changes. However, this changing torque is counteracted by a changing spring force F. Thus an increased torque is counteracted by an increased spring force F exerted by the coil spring 13 due to being coiled more tightly. By proper dimensioning of the spiral peripheral surface 14, the torque can be arranged to counteract the spring force F so that a substantially constant traction force is applied to the patient's skeletal structure how ever much the elongate member 15 is unwound.Thus during a period of traction the patient is able to move slightly, causing the amount that the elongate member 15 is wound around the wheel 8 to change, without affecting the traction force exerted by the de- vice 1.

The spring force F applied to the coil spring 13 can be adjusted by pre-setting the wheel 24. There is sufficient friction in the adjusting mechanism and the mounting of the spring casing 10 to ensure that the spring casing 10 remains in a set position relative to the base 2 after a setting operation and during subsequent use of the exercising device.

Although the traction device 1 is particularly suited as a medical traction device, the invention is not intended to be limited to such a use and can be employed in other types of traction devices. For example the invention can be employed in an exercising device where repeated movements, e.g. pulling movements, are made against an opposing force provided by the spring means.

In the embodiment described the elongate member 1 5 has been shown connected to the peripheral surface 14. However it should be realised that it could be attached to other parts of the wheel 8 in such a manner so as, in use, to be wound at least partially around the surface 14. For example a slot, e.g. a radial slot, could be provided in the wheel, the slot having an enlarged inner end and an outer end opening into the peripheral surface 14 at its outer end 14a. In this case the elongate member 1 5 could be fixed within the slot, e.g.

by providing the elongate member with an enlarged end received in the enlarged inner end of the slot.

Claims

1. A traction device comprising support means, reel means turnably supported by said support moans, spring means providing a spring force for urging the reel means, in a first rotary direction, into a first position, a flexible, substantially inextensible elongate member extending around at least part of the periphery of the reel means when the latter is in its first position and having one of its ends attached to the reel means and the other of its ends arranged so that it can be pulled to turn the reel means out of its first position, in opposition to said spring force, in a second rotary direction opposite to said first rotary direction thereby to at least partly unwind the elongate member from the reel means, wherein the traction device further comprises adjustment means for enabling pre-adjustment of the spring force exerted by the spring means.

2. A traction device according to claim 1, in which the elongate member is wound through an angle of less than 360O around the periphery of the reel means when the latter is in its first position.

3. A traction device according to claim 2, in which the reel means is in the form of an eccentric wheel arranged so that the distance from the point on the periphery of the wheel at which the elongate member leaves contact with the wheel periphery to the turning axis of the wheel increases as the reel means turns in said second rotary direction.

4. A traction device according to claim 3, in which the eccentric wheel is so designed that the traction force generated by the traction device is substantially constant however much the flexible elongate member is unwound from the reel means.

5. A traction device according to any of the preceding claims, comprising stop means for preventing turning of the reel means in said second rotary direction past a second position.

6. A traction device according to claim 5, in which the reel means is turnable through an angle of less than 360O during movement from its first position to its second position or vice versa.

7. A traction device according to any of the preceding claims, in which the spring means comprises a spirally wound spring.

8. A traction device according to claim 7, in which said spirally wound spring has one of its ends fixed relative to the reel means and in which the spring adjustment means comprises a rotatable member to which the other end of said spring is fixed which is adjustably turnable relative to the reel means to adjust the angle through which the spring is wound for adjusting said spring force.

9. A traction device according to any of claims 1 to 6, in which the reel means is fixed to an axle turnably mounted in the support means, the spring adjustment means comprises a casing surrounding, and turnable relative to, the axle, and the spring means comprises spring material spirally wound or coiled about the axle within said casing and having one end fixed to the axle and the other end fixed to the casing.

10. A traction device according to claim 9, in which the adjustment means further includes a manually adjustable setting wheel for setting via gearing the position of the casing.

11. A traction device according to claim 10, in which the casing is provided with a worm wheel meshing with a worm turned by said setting wheel.

12. A traction device according to any of claims 9 to 11, comprising stop means for limiting turning of the casing.

13. A traction device according to any of the preceding claims, comprising indicating means for providing an indication representative of the spring force pre-set by the adjustment means.

14. A traction device constructed and arranged substantially as herein described with reference to, and as illustrated in Figures 1 and 2 of the accompanying drawings.

15. A medical traction device for traction of a patient's bones and/or skin, the device being as claimed in any of the preceding claims.