Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Patent
1997-05-13
1999-08-17
Jeffery, John A.
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
744248R, 74459, F16H 2702
Patent
active
059376996
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a telescopic system.
2. Description of the Related Art
Telescopic systems include mechanisms constituted by several modules which, at random, can be unfolded/extended or folded in one another, or optionally alongside one another in order to regulate their total length.
Telescopic systems are encountered in numerous technical fields such as cranes, ladders or appendages of robots in order to reach an object having a variable distance or for other functions, specific to each apparatus in which they are incorporated. In the case of robots walking on a series of legs distributed into two sets and which alternatively touch the ground in order to support the robot and are then raised and advanced, telescopic mechanisms equipping the legs in order to shorten and lengthen them make it possible to achieve this procedure in a simple manner, because it is merely necessary to slide the legs along the robot in order to advance the same once they have been raised from the ground. The legs can remain straight and it is pointless to subdivide them into sections articulated to one another and to the robot in order to attempt to reproduce human walking procedure, which requires a more complex structure and causes balance problems.
A first distinction will be made by only attaching interest to mechanisms for which the extension path is greater than the length of the mechanism in the folded state, which imposes the use of at least two modules having an extensible elongation element (such as a sliding tube) and a mechanism joining said elongation element to a preceding elongation element or to a fixed element serving as a base for the mechanism in order to vary the distance separating them and thus controlling the extension of the elongation element. The system is then complicated by the need of adding mechanical links for joining the mechanisms in order to control simultaneously or successively the extension of all the elongation elements.
A current telescopic system used for certain hydraulic cranes consists of several concentric tubes interconnected by jacks arranged in series and communicating with one another by fluid pipes, so that a single pressure source can successively extend them. The control is then ensured by a single action. A multiple action, single jack, i.e. formed by several fitted together, sliding cylinders can also be used with the same advantage. However, jacks are relatively heavy and cumbersome means, which also require flexible supply cables and sensors complicating their installation. Thus, this solution cannot be used in applications such as robotics, where the aim is to reduce to the greatest possible extent the overall weight of the system and the overall dimensions of the control and monitoring means.
A completely different system consists of providing the extension elements with pulleys and cables interconnecting them forming zig-zags. It is sufficient to pull on one cable end in order to simultaneously raise the elements. This system, used for certain ladders and elevators, is characterized by a lack of rigidity, which can be vital for firefighters or furniture removers who have to dock the ladder with a building, but which is unacceptable in other applications, having the disadvantages of limited loading capacity and a problematical behavior of the cables and pulleys over time.
A more complicated system although relatively simple to construct, which has a relatively low weight and a good rigidity, is described with the aid of FIG. 1. It has been used in a robot and consists of three extension modules 1a, 1band 1c, whereof each comprises a screw 2, a nut 3 engaged with the screw 2, an entry pulley 4 fixed to the rear end of the screw 2, an exit pulley 5 fixed around the nut 3 and coaxial thereto, a screw bearing surface 6 towards the rear of the screw 2 but in front of the pulley 4, a nut bearing surface 7, a rear stop 8 located on the screw 2 just in front of the screw bearing surface 6 and a front stop 9 located we
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Commissariat a l''Energie Atomique
Fenstermacher David
Jeffery John A.
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