Actuator

Abstract

An actuating device formed of elastic tubing having circumferential reinforcement therein and having a portion of the transverse periphery with longitudinal cords of tension resistant material along only one side of the tubing. In the relaxed state the device is substantially linear, but upon introduction of a pressurized fluid therein the tube curls about the side having the longitudinal reinforcing cords and upon release of the pressurized fluid the device returns to substantially a linear state.

Description

BACKGROUND OF THE INVENTION

Hydro-mechanical actuators are commonly used for providing movement through limited distances. Examples of such devices are to be found in equipment for handling materials at elevated temperatures, at cryogenic temperatures and where high levels of radioactivity preclude human operators from close proximity to the material being handled. Such actuators are also used to provide force assistance for moving linkage members and other components of machines and manipulative devices.

One area of possible use for such devices is that of providing a means of assisting persons who, through physical affliction, have lost partially or completely the use of some of their bodily limbs. Various mechanical expedients have been devised to provide aid in operatively moving incapacitated bodily limbs, but these expedients have been unwieldy and difficult to maintain in proper working order due to their mechanical complexity. Heretofore, such devices have utilized arms and pinned linkages capable of providing limb assist by translatory motion and rotational movement about pivot pins. In order to get accurate and repeatable multi-directional motion from such mechanisms, the components must be intricately designed and must be made with a high degree of precision and are, therefore, quite costly.

Furthermore, the bulkiness and weight of mechanical actuators for aiding the motion of human limbs is often a source of annoyance and embarrassment to the patient "wearing" the devices, in view of the unsightly appearance of the complex of linkages and pinned connections. In order to avoid the embarrassment of wearing such orthostatic or prosthetic devices, many persons suffering from partial or total loss of use of some limbs prefer instead to remain without the full use of their limbs.

SUMMARY OF THE INVENTION

This invention relates to a fluid pressure operated actuating device for providing movement through limited distances. The invention is in the form of an elongated flexible tube having a longitudinally extending opening closed at one end, the tube being easily and freely flexed in its natural or linear state, but assuming an arcuate configuration about an axis substantially at right angles to its length upon introduction of a pressurized fluid into the opening. This action is the result of the tube having a portion of its transverse periphery of lesser longitudinally extensibility than the remainder of the periphery. In the preferred embodiment this is made possible by forming the tube of elastomeric material with substantially inextensible longitudinally extending reinforcing cords disposed therein in a region which does not exceed one-half of the transverse periphery of the tube. The tube preferably also has substantially inextensible reinforcing cords radially inward of the longitudinal cords and extending at right angles to the length of the tube. The layer of longitudinal reinforcing cords along one side restrains the device, such that upon internal pressurization, the device changes from a linear configuration to a curved state with the side having the tension cords therein forming the radially inner surface of curvature.

The device has a variety of uses one of which is attachment to disabled or handicapped human limbs for inducing motion thereof by selectively internally pressurizing the device to produce the desired amount of curvilinear motion and hence movement of the attached limb.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the actuator with the end portions broken away to show the terminal fittings; the device being illustrated in full lines in its curled pressurized state, and the unpressurized configuration being indicated in dashed lines; and

FIG. 2 is an enlarged transverse section taken along the section-indicating lines 2--2 of FIG. 1.

DETAILED DESCRIPTION

Referring now to FIG. 1, the presently preferred embodiment of the actuator 10 is shown in actuated condition wherein the tube 11 is pressurized internally by a fluid. The tube 11 is in the form of an elongated elastically flexible tube having one end closed. The tubing has an opening extending longitudinally therethrough, which opening is closed at one end. A longitudinal portion, not exceeding one-half the transverse periphery of the sidewall thereof, is made of a material which has the property of being longitudinally inextensible. The remainder of the tubing 11 is made of extensible material. Upon introduction of a pressurized inflating fluid through the opening in the tube, the tube is caused to curl about an axis perpendicular to its longitudinal direction.

In the preferred form of the invention, the tube 11 is made of elastomeric material, with the inextensible portion comprising longitudinally extending reinforcing cords 15 embedded in the sidewall of the tube. One end of the actuator is closed, preferably, by a plug means 13 securely fastened in the bore of the tubing 11. In the preferred form of the invention, the actuator 10 is fabricated and vulcanized in the substantially linear state shown by the dashed lines in FIG. 1.

Referring now to FIG. 2, the carcass of the tubing 11 is shown in a cross-sectional view. The tubing has a polygonal shape in the preferred form with preferably two opposite parallel sides 11a and 11b. The reinforcing cords 14 comprise at least one layer embedded closely adjacent the inner periphery of the tubing. The cords 14 are disposed substantially perpendicular to the length of the tubing and are preferably in equally spaced parallel relationship with each cord extending continuously around the wall of the tubing with the ends of the cords overlapping each other to form a splice. In the presently preferred form of the invention, the cords 14 are made of stranded textile fibers, but the cords may also be made of monofilamentary material, or from stranded metal filaments where high pressures are required for actuation.

Embedded radially outwardly of the circumferential cords 14 is a substantially planar layer of longitudinally extending parallel cords 15, with each cord running continuously the length of the actuator. The cords 15 are preferably disposed radially outward of the cords 14 in a layer which extends transversely the width of one of the parallel sides 11a of the polygonally shaped tube 11. The cords 15 provide resistance to elongation for the side 11a when the tube 11 is pressurized internally. The opposite side 11b of the tube is permitted to elongate when the tube 11 is pressurized internally and the tube carcass 11 tends to curl or coil about the side 11a. Thus, the actuator 10 may, by introduction of a fluid at sufficient pressure therein, be caused to assume the configuration shown in FIG. 1.

A port means 12 is provided for introducing pressurizing fluid therein. In the preferred form of the invention illustrated in FIGS. 1 and 2, the port means 12 is a small rigid tube 12, having a bore diameter smaller than the opening in the tube 11, which rigid tube 12 is securely fastened and sealed therearound in one end of the tube 11 in a manner effecting a fluid pressure-tight seal such that fluid passage is allowed only through the port means 12. Upon releasing the pressurized fluid from the interior of the tubing 11, the actuator uncurls due to the elastic nature of the tubing material to assume again a substantially linear configuration as shown by the dashed lines in FIG. 1. The actuator is thus substantially linear in the de-actuated or unpressurized state, curls upon pressurization, and returns to the uncurled linear state again upon de-actuation without the aid of any external force assistance.

Although this novel actuator will readily lend itself to many and varied uses, the particular application of the presently preferred embodiment is a prosthetic device. When the actuator is attached, for example, along a bodily limb with the inextensible side 11a contacting the surface of the limb and extending along the outside of one or more joints, for example the knuckles of a finger, the limb may be moved by pressurizing the actuator and causing it to curl. As the internal pressure is subsequently released from the tubing, the actuator no longer tends to curl about the tension resistant side 11a, but returns to its original linear configuration, thus tending to straighten the limb.

The present invention thus comprises an actuator formed of flexible material preferably elastomeric tubing having a polygonal cross-section with tension reinforcement cords embedded longitudinally along only one side which cause the actuator to curl about an axis perpendicular to the length of the actuator when pressurized internally. However, it is not a requirement of the invention that the tubing 11 have a polygonal cross-section or that there be two opposite parallel sides and the tubing may have a generally closed curvilinear shape, or any polygonal shape, as for example triangular. Furthermore, the tubing of the actuator need not be made of elastomeric material. Any suitable fluid impervious material may be used which is capable of elastically returning to the linear configuration in the unpressurized state without the aid of external force assistance.

Persons having ordinary skill in the art may see further adaptations and modifications to the invention which is limited only by the spirit and scope of the appended claims.

Claims

I claim:

1. An actuating device comprising: an elongated elastic tube having an opening extending longitudinally therein with one end closed and adapted to have fluid under pressure introduced therein, the said tube being formed of elastomeric material with at least one tension layer having a plurality of longitudinally extending substantially inextensible weftless reinforcing cords embedded therein and with the said layer extending transversely of the tube less than one-half of the transverse periphery thereof to provide a region having lesser longitudinal extensibility than the remainder of the periphery so that the tube is caused to assume an arcuate configuration about an axis at substantially right angles to its length upon introduction of a pressurized fluid into said opening.

2. The device defined in claim 1, further comprising at least one ply of substantially inextensible reinforcing cords disposed circumferentially and radially inward of said tension ply with each cord extending around the tube at substantially right angles to the tube.

3. The actuating device defined in claim 1, wherein the said tube has a polygonal transverse section with two opposite parallel sides with the said tension cords disposed in only one of the said parallel sides.

4. The device defined in claim 1, wherein the cords in said tension ply are made of stranded metal filaments and the said circumferential cords are made of textile material.

5. The device defined in claim 1, wherein the cords in the said tension ply and the circumferential cords are made of stranded metal filaments.

6. The device as defined in claim 1, wherein

a. the said opening is a continuous bore through the length of said tube,

b. the said closed end is provided by plug means inserted in one end of said bore, and

c. a fluid port means is provided in the other end of said bore, which port means is adapted to be connected to a source of fluid under pressure.

7. An elongated tubular body comprising a structure which is limited against circumferential extension substantially uniformly throughout its length, a longitudinal section of said structure being limited against extension in the longitudinal direction, the remainder of said structure being reversibly extensible in said longitudinal direction, whereby inflation of said structure with a fluid will cause said structure to flex.

8. An elongated tubular body comprising a flexible structure, means for limiting said structure against circumferential extension substantially uniformly throughout its length, means for limiting a longitudinal section of said structure against extension in the longitudinal direction, the remainder of said structure being reversibly extensible in the longitudinal direction, whereby inflation of said structure with a fluid will cause said structure to flex.

9. A tubular body according to claim 8 in which said means for limiting against circumferential extension comprises elongated substantially non-extensible material oriented transversely to said longitudinal direction in restraining relation with the walls of said body.

10. A tubular body according to claim 8 in which said means for limiting said longitudinal section against extension comprises flexible but substantially non-extensible material oriented in said longitudinal direction in restraining relation with said longitudinal section.

11. A tubular body according to claim 8, in which said structure is a tube of flexible elastic material, and said limiting means are cord-like members of substantially non-extensible material.