Static structures (e.g. – buildings) – Striplike unit – reversibly flexible and rigid
Patent
1996-05-03
1998-06-16
Kent, Christopher
Static structures (e.g., buildings)
Striplike unit, reversibly flexible and rigid
E04H 1218
Patent
active
057653208
DESCRIPTION:
BRIEF SUMMARY
This invention relates to mechanical actuators, and more particularly to a linear actuator for producing linear motion from rotary motion.
There are many practical applications that require linear motion, such as actuators for sliding doors, door openers, car windows, throttle actuation, car seats, trunk lids, aerospace equipment, and robotics.
Numerous prior art techniques are known for providing such linear motion. These can generally be divided into two classes, namely systems that have a rotary drive motor connected to some form of linkage, such as a crankshaft or Archimedes screw to produce the linear motion; or linear drive systems, such as hydraulic or pneumatic rams, or linear motors that produce the linear motion directly.
All these prior art devices have in common the fact that they result in complexity of moving parts, undue weight, space inefficiency and high cost.
U.S. Pat. No. 3,319,987 describes an extendible boom for such applications as lifts, antennas, elevators, manipulators and the like. This patent describes a coiled flat ribbon that can wound off a drum into an extended load-supporting tube. While this patent describes a device that has important practical applications, it is not suitable for applications that involve the repetitive reciprocation undergone by a linear actuator because such repetitive motion weakens the ribbon, and where it comes off the drum it tends to flex. As a result, play between the drum and collar rapidly develops, and reliable and precise extension of the arm become impossible.
An object of the invention is to provide a simple device for providing linear motion in an efficient and reliable manner.
According to the present invention there is provided a linear actuator comprising a drum, a stiff flexible ribbon windable onto the drum, drive means for rotating the drum so as to alternately wind and unwind the ribbon onto and off the drum, a shaped guide arrangement adjacent the drum for gradually forming the ribbon leaving the drum into a tubular configuration, and attachment means at a free end of said tubular configuration for connection to an object to be moved in a linear path. The shaped guide arrangement is a tapered funnel having a shallow widened portion adjacent the drum and progressively merging into a tubular portion forming an outlet for the ribbon. The tapered funnel conforms to the shape of the ribbon as it is gradually formed into a tubular configuration. A spring-mounted retainer strap extends around the drum and remains in contact with the ribbon as it is wound onto and off the drum.
The tubular configuration can have varying cross-sections, such as round or oval, and it is not necessary for the edges of the ribbon to abut. The tube must merely have sufficient curvature to give it the desired degree of compressive strength. In a preferred embodiment of the invention, suitable for applications where a long reach is required, such as aerospace, the edges of the ribbon are designed to interlock such that the edges join together zipper fashion as the tube emerges from the funnel.
In accordance with the invention, the portion of the ribbon formed into a tubular configuration serves as a push rod for imparting linear motion to the object. Because of its tubular shape, it attains considerable axial compressive strength. Preferably, the ribbon is extruded in tubular shape, so that inherently it has this configuration and naturally tends to take up a tubular shape due to memory effect as it comes off the drum.
The ribbon can be conveniently made of resilient plastic or metal. A suitable ribbon, for example, might have a width of 5 cms. and a thickness of 0.5 mm.
The drum is normally driven by a drive motor, which may be mounted either behind the drum, inside the drum, or underneath the guide means and connected to the drum by means of a drive chain. Alternatively, the drum could, for example, be connected to a hand crank if manual operation of the actuator were desired.
The guide arrangement is preferably formed into the shape of a funnel having a flat wi
REFERENCES:
patent: 3319987 (1967-05-01), Bohr et al.
patent: 3360894 (1968-01-01), Sharman et al.
patent: 3601940 (1971-08-01), Simon
patent: 3696568 (1972-10-01), Berry
patent: 3811633 (1974-05-01), Cummings et al.
LandOfFree
Linear actuator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Linear actuator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Linear actuator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1713981