Newsgroups: comp.robotics
Path: brunix!uunet!europa.eng.gtefsd.com!howland.reston.ans.net!spool.mu.edu!umn.edu!csus.edu!netcom.com!nagle
From: nagle@netcom.com (John Nagle)
Subject: Re: Opening/Closing Actuators
Message-ID: <nagleCB1HGv.v8@netcom.com>
Organization: NETCOM On-line Communication Services (408 241-9760 guest)
References: <mott.744001905@sfu.ca> <1993Jul31.082328.29375@osuunx.ucc.okstate.edu>
Date: Sat, 31 Jul 1993 17:19:43 GMT
Lines: 34

In article <mott.744001905@sfu.ca> mott@malibu.sfu.ca (Jennifer Anne Mott) writes:
>Hello
>
>I'm trying to find some kind of actuator that could be used to both open and
>close something shaped vaguly like the petals of a flower.
>
>I'd prefer something that would move from one state to the other (i.e. from
>opening to closing) WITHOUT having to "reverse" or change the inputs.  (sort
>of like the auto reverse on a tape deck automatically starts to play in the
>other direction without human intervention.  Here I want something that does
>that without "electronic" intervention ... if that makes any sense)

      Can you say more about the application?  It's not clear whether you
want to actuate something the size of a flower or the size of a 
power shovel clamshell bucket.

      Mondo-Tronics makes a "memory metal" actuator, and they have a
demo unit which slowly and quietly flaps the wings of a decorative bird
model.  That's at the low end of the power range.

      At the high power end, you can get auto-reverse mechanisms using 
spool valves for pneumatic and hydraulic systems.  Jackhammers
and impact wrenches use that arrangement.  You can buy the valves and
cylinders separately, or get integrated assemblies.  Slow and fast
moving systems are available.  Call a pneumatics dealer for info.

      There are hundreds of mechanical linkages that have been designed
for producing reciprocating motion.  This was a classic problem of the
steam-engine era, and any book on mechanism design will have some samples.
Many are variations on the crank, but there are some wierd ones.
Outfits like Small Parts Inc. and Berg sell standard mechanisms for
various motions.

					John Nagle
