Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1990-11-19
1993-06-08
Ip, Paul
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
31856818, 318646, 901 29, 901 21, G05B 1942
Patent
active
052182800
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention is concerned with an actuator whereby controlled movement can be achieved. One important area where such an actuator will be of particular use is in the construction of articulated joints, such as in robotic arms.
BACKGROUND OF THE INVENTION
Robotic joints are commonly operated by electric motors and associated drives, chains, flexible cables, pneumatic or hydraulic pistons, or shape memory alloys. These joints and actuation methods are either bulky, limited in directional capability or expensive in terms of energy. The current actuation methods are incapable of reproducing the versatility in movement of the human body which they are trying to imitate.
SUMMARY OF THE INVENTION
According to the present invention there is provided an actuator comprising an inflatable chamber member having mounting means at one end and a high tensile fibre connecting-link at the other end, the fibre extending along a wall of the chamber member such that expansion of the chamber member will cause the combined length of the chamber member and link to be decreased.
In one preferred construction the chamber member is bladder-shaped and is defined by the combination of one wall which is substantially inextensible and a further wall which has the fibre embedded therein. Alternatively the chamber member may be defined by a collapsible cone having a closed base, with the connecting-link fixed to an edge portion of the cone base and running freely across the face of the cone base and through a guide hole. The guide hole could be defined by a loop fixed to another edge portion of the cone base. Alternatively the guide hole may be defined by a hole in a plate to which the chamber member is attached. Advantageously the connection of the connecting-link to the cone extends back by a fibre or flap across the conical wall of the cone.
The chamber member may be formed from natural or synthetic rubber material, for example nitryl, neoprene, butyl and silicon rubbers, polyurethane, polyethylene, polystyrene and hypalon. Ideally the walls of the chamber member will incorporate reinforcing fibres.
The connecting link can be a single fibre or a bundle of fibres formed from glassfibre, carbonfibre, metal wire, natural or synthetic woven threads or other high tensile fibrous material.
The invention further extends to an artificial joint comprising a pair of pivotally interconnected arms with an actuator of this invention as hereinbefore defined connected between the two arms by the mounting means and the connecting link.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be performed in various ways and preferred embodiments thereof will now be described with reference to the accompanying drawings in which:
FIG. 1 is a side view of a robotic joint incorporating an actuator of this invention;
FIGS. 2 and 3 are sections on lines X--X and Y--Y of FIG. 1;
FIGS. 4 to 6 are illustrations of three variant forms of an alternative type of actuator of this invention; and
FIG. 7 is an illustration of a linear sensor which can be used in the robotic joint shown in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
The embodiment illustrated in FIGS. 1 and 3 comprises an actuator 1 which is associated with an articulated joint defined by a pair of arms 2 and 3 which are pivoted at 4. The actuator comprises a bladder-shaped chamber 5 whose one end is secured to the arm 2 by a mounting 6, whilst a bundle of fibres 7 extend from the other end of the chamber member 5 to a junction 8 on the other arm 3. The rear wall 9 of the chamber member 5 is formed from woven bi-directional fibres 10 whilst the outer wall is defined by an array of high tensile fibres 11, at least some of which extend from the fibres 7. Fibres 7. 10 and 11 are embedded in elastic material.
When a pneumatic or hydraulic fluid is pumped through an inlet 12 to the chamber member 5, the latter expands and the fibres 11 bow outwardly, thus pulling on the fibres 7 and raising the arm 3, with the respect to the arm 2, to lift a weight 13. When the fluid is
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