Tom Shelley reports on a device that could
revolutionise linear actuation in a very wide range of products
In a novel actuator, a chain of links in a guide are coiled round
in such a way as to form a strong, rigid rod, which emerges at 90
degrees to the chain guide.
Exceptionally ingenious, its Danish developers have named it the
'Kataka', Sanskrit for golden chain, in the hope that it will
yield appropriate profits.
It requires very little space in its direction of actuation when
retracted. It therefore offers benefits to designers of a vast
range of products from window openers through hospital bed height
adjusters to car jacks.
Soren Jensen, of promoters, VKR Holding, based in Copenhagen,
told Eureka that Jens Sorensen, its inventor, was inspired by the
feeding of cartridges into machine guns. The original intention
of the invention was to devise an improved window opener whose
mechanism could be concealed in its frame.
Locking chains have been made before, and the 'Indian rope trick'
with slats locked together by a tightened cord has been known for
centuries. Previous designs, however, have tended to lack
something in their load carrying capacity when free standing,
which is why the rope trick was only ever performed with a small
boy climbing it.
The secret of the new device lies in its links. These are
parallelogram shaped, with a hook shaped hinge member at each
end. Each link is made up of two elements that can slide over
each other in a direction parallel to the axes of the hinge
members. The inner elements possess helical grooves on their
insides, and the outer members, curving grooves on their
outsides. Each inner element also has a tongue at one end, and a
fork at the other.
In unextended mode, the links sit in a rectangular guide,
linked by their hook shaped hinge members. They are drawn into
the actuator assembly device by an advancing wheel with helical
protuberances that fit into the helical grooves on the insides of
the links. Fixed protuberances on the inside of the assembly
device fit into the curving grooves on the outsides of the outer
elements, guiding them into position.
When the links are fed into the assembly device, they are turned
relative to each other so that the hook shaped hinge members
engage fully with each other. At the same time, the links slide
relative to each other so that the parallelogram links form a
continuous, long parallelogram, coiled into a spiral. Because the
inner and outer elements of each link are displaced relative to
each other, the boundaries between adjacent inner elements and
outer elements are similarly displaced relative to each other,
giving the formed rod rigidity. This is enhanced by engagement
between tongues and forks at each end of the inner elements.
The device presently exists in the form of a working proof of
concept prototype. This extrudes a rod of 18mm diameter and has a
maximum stroke of 500mm. In its retracted position, it has a
height of 35mm. Speed is 3mm/s and the machine has so far been
put through 10,000 cycles, lifting a 50kg load. Maximum dynamic
force is 250kgf.
The prototype draws its chain links from a rectangular guide,
but they could be stored in containers of many shapes, including
coiled configurations, requiring little space. The hollow central
core of the extruded actuator offers a space for wires, tubes or
cables.
The idea is patented or has patents applied for in various forms
and configurations and in all "Significant markets."
The developers and promoters are looking for partnerships with
companies able to turn the prototype into a family of industrial
products. Partnerships could take the form of joint venture
agreements, licensing or marketing. Potential markets have been
identified in satellites, aerospace, the automotive sector,
furniture, hospitals, the military, automation and special
purpose machines.
Used as car jacks, the devices could be built into a vehicle
chassis, so the car could be raised off the ground for a tyre
change at the touch of a button. This would be most useful in a
world where many drivers are unable to use a conventional jack
while others cannot be relied on to use one at all safely. For
large commercial vehicles, including cranes and construction
equipment, the units offer a sleeker and tidier way of making
stabilisers. They could also simplify the construction of
caravans and campers that have extendible or liftable sections to
allow the provision of maximum space when stopped, while causing
minimum wind resistance when driving.
Being light and portable, it has been suggested that they might
be used in avalanche rescue equipment. By heating the tip of a
drill on the end, it could quickly reach a buried person,
presumably located by GPS, allowing the supply of oxygen and
other vital supplies. For the same reasons of lightness and
compactness, the actuators offer promise in shop window and
exhibition trade stand displays.
In security applications, extended rods could be made to protect
windows and doorways. Door openers could be made more discrete,
with the mechanism concealed in the frame and new kinds of blinds
designed that could extend from one side, or rise from below. As
awning extenders, the actuators offer the possibility of running
lighting cables down the centres of the rods, protecting cables
as well as making them look tidier. They have also been suggested
as suitable for the rapid erection of military tents and mobile
hospitals. Banners, tables and road signs could all be made to
extend outward from walls or ground. Disappearing bollard lamps
could be made that would not require the digging of deep holes.
Queue divider posts in airports or posts for tennis or volleyball
nets in sports halls could be erected instantly when required.
Chairs and beds could also be easily height adjusted using
compact mechanisms hidden in framework. It has further been
suggested that wardrobes or clothes shop racks could be made with
extendible rods for hangers. Kitchen drawers could be
electrically opened or closed or work surfaces raised or lowered,
to suit the needs of the disabled or lazy. Cooker hoods could be
made to disappear or fold behind appliances when not required as
could loudspeakers, television and other items of furniture. Many
other applications are also possible, limited only by designer's
imagination.
VKR-Holding
or email Soren Jensen
Pointers
* Special links are coiled into a spiral to form a strong, rigid
rod
* The links can be stored in a container of arbitrary shape or
within a window or door frame or vehicle chassis member
* The device exists as a working proof of concept prototype
For more technical developments see www.eurekamagazine.co.uk