Publication history, Reflections & comments
It is largely a development of time-and-motion study, but the main emphasis now is on human abilities, and the man-machine interface. This is important in all types of work, and of double interest to doctors and engineers, who may be involved in design as well as usage.
Simple examples are the layout of controls of a lathe or the shape of an observation cabin in a steel mill. The field is well-covered in books such as "Ergonomics" by Murrell or those on Human Engineering, and by experts in the NSW Division of Occupational Health. On the occasion of this lecture the speaker will concentrate with personal work dealing with handle design and hand function.
HANDLES. A suitable example for discussion is the round knob tightened to secure height on a surgical instrument table. Because of the round shape, tightening is difficult and the table height can suddenly collapse. In any case its use involves unnecessary muscular strain. A simple and logical modification is the brazing of a transverse bar, which increases applied torque through its shape rather than the diameter. Similar considerations apply to other items to be tightened by hand - screwdrivers, knobs, taps, and lids of many kinds. Torque measurements for tightening cylinder head bolts are second nature to engineers, but torque measurements or -.-.he human operator with different styles of equipment are an unknown matter, so far.
Another example from surgery is the Deaver retractor, a standard instrument used to hold tissue out of the field of view during deeper operations. This has a thin strip of metal for a handle, is tiring for the assistant to hold, and may impair his dexterity for an hour or two. Interesting confirmation of the extra strain comes from electromyography. Similar principles of handle design apply to most types of tool held in the power grip of the hand.
NEEDLEHOLDERS are the surgeon's equivalent of the engineer's pliers, and their design can be analysed in terms of details of the grips of the hand. These ale the power grip, two types of precision grip (pen type and fork type) and a storage grip. Hitherto, rotation of the needleholder has needed forearm rotation. With a cylindrical palmar handle and a cone for the thumb, the instrument can be rotated 180 degrees within the hand, with the advantage of anti-tremor support or added range of movement and position.
TRIGGER FUNCTION, exemplified by needleholders or pliers, is a movement of one part of a tool by one part of the hand, relative to the rest of the tool. Examples comprise guns (index finger), end-button or torch-switch (thumb), and tweezers (thumb and index). Precision is given by the index, but the thumb has greater power, reflected in Professor Tichauer's design for power tool switches. Remote control devices have been tried for very delicate work.
HANDLE STIFFNESS OR RESISTANCE can also be a limiting factor due to poor design for the average human operator, whether for surgical needleholders, tin-snips, or nut-crackers. The appropriate measurements are easy to make.
MICRO WORK is expanding both in surgery and electronics, apart from the established watchmaker's craft. Two vital requirements are a mechanical or anatomical fulcrum close to the work, and visual feedback with enough magnification and correct lighting. Sense of touch and pressure become of diminishing help. ("kinaesthesia").
ERGONOMIC ATTITUDES, bridging the inter-disciplinary gap, can help both engineer and surgeon in the future. Lectures, discussion over coffee and biscuits, and mutual visits to places of work - greasy workshop or blood- stained operating theatre - promise widespread benefit, as each adapts to the normal work surroundings of the other.
Handle stiffness or resistance
Engineers, doctors, and ergonomics
Lecture to the Association of Certificate Engineers, at Newcastle Technical College 31 July 1969 Michael Patkin
At this time I was Fellow in Surgery at the Royal Newcastle Hospital, mentioned elsewhere on this website. Like my other talks over the years, this one was accompanied by 35 mm slides. In time these will be added, or linked to them on this website.
Today  it is even more important than ever to get the message of ergonomics through to engineers, designers, and entrepreneurs.