Kinkajou Design Journal

Wind-up browsers should be optimized to work entirely mechanically (e.g., they use sunlight or external powered light sources such as ordinary lamps as light sources, and do not include LEDs or any other built-in source directly). This does not rule out the design of 'dedicated' lighting sources, but these would not be part of the 'basic' browser. The browser itself would have standardized attach points, clip locations, threaded fittings, etc. for alternative designs of light source.

It should not be difficult to design a set of plastic mechanism parts that will step the tape and/or the 'objective lens' or 'sled' so that fine page advance and navigation can be done with push buttons instead of cranks. This is especially necessary for small hand-held devices, where the ergonomics of working a pair of cranks isn't particularly good. Note that the View-Master projectors inherently possess this kind of system, but only as an advance; this would not be particularly useful for many types of microfilm presentation, particularly those being viewed at magnifications high enough that only part of a page is visible in the viewing window (good example being any microformed newspaper page!) The indexing system has to have positive stepping in at least the four cardinal directions of navigation, which may imply two different "transmission" systems (one for the cranked film transport, and one for lateral stepping of the optics). Imho, these mechanisms should be designed so that simple user adjustments could vary the amount of movement produced with each click. I also think it might be nice (but less 'essential' if building to a price is a key design component) to have a second set of controls that do coarser (or quantized-to-page-boundary) motion.

I had, at one time, considered the use of positive-location stops (holes or perforations in the filmstrip at key locations) to facilitate this kind of navigation, but the cost of preparing the film is not justifiable unless specialized laser equipment can be provided.

A couple of other wind-up browser "optimizations":

1) Use a long plastic spring to pretension the device, and another one which is 'wound up' as the film is advanced. A simple arrangement of clutches then gives the benefit of positive rewind when done.

2) Any browser using a powered light source can have motorized transport at little additional cost. You would use some combination of electrical charging technologies, but providing a crank on the browser's permag motor would allow it to serve as a primary generator (ostensibly for the light source), removing the need for photovoltaics (etc.) while maintaining cost justification for powered transport...

3) A windup browser that would work with microfilm in a 'standard' cassette headshell should not be markedly difficult to design, and potentially simplifies procurement of some key devices (for example, ordinary cassette winders can be used both for rough cuing of long tapes and for effective soft rewinding for storage or next use. The amount of hand cranking needed in a school with any great number of these devices would rapidly exceed the available time of teachers... whereas a simple gang winder with through shafts and slip clutches would provide an effective way to rewind/re-index large numbers of cassettes in a short time with little foreground attention.

Posted by: R.M.Ellsworth at March 6, 2004 06:52 PM