Page 263 - My FlipBook

HISTOBY OF DENTAL SUEGEEY 231

The development of this "flexible joint coupling" is still in constant use
in the engine cables and flexible wrist joints.
"The third division, or class of dental drilling and rotary cutting mechan-
ism commences with G. F. Green's pneumatic engine. This appeared about
18G8, and was quite generally used at one time by dentists, especially those of
the western states. The apparatus was worked by a foot bellows, tlie air
from which proceeded through a rubber tube to the hand ])iece, where it pro-
pelled certain mechanism which rotated the drill.
"The next to appear on the scene, and the first of the 'standard' class
of engines, was the 'Morrison,' about 1870-71. Dr. G. V. Black, then in
Jacksonville, 111., made and used a somewhat similar "standard" engine, which,
however, was not manufactured for sale.
"There are traditional accounts of a pedal engine invented and used by
Dr. John B. Beers, of Eocliester, N. Y., as far back as 1842. It is said that
this engine also worked by a coiled steel universal joint. Of this, however,
there are no published records; and it can hardly be justly included in the list
of dental appliances, especially as it was never used by any except tlie inventor.
The Morrison was the first offered to the general profession, and was very
quickly and widely adopted. For some years it had no dangerous com-
petitor.
"In 1871 was patented Elliot's 'suspension' engine. This apparatus pre-
sented entire novelty in all things except the fact of the power being still pedal.
The hand-piece and tool-holder, susjjended by a cord, which was also the driv-
ing cord, by swinging freely in all directions avoided the necessity of a uni-
versal joint. The cord was kept tight on the tool-pully by an equalizing
weight and wheel, and the pedal and driving-wheel could be in any position."
The suspension engine, in some of its forms, is still used and preferred
by many dentists.
"The last, 'but not the least' of the 'standard' engines is the S. S. White.
In this the free movement of the hand-piece is obtained by making the whole
arm flexible through constructing it of a wire rope of spring temper. At first
the strands of the rope were all twisted in one direction ; whereby, when hard
pressed, ensued what was called 'back lash'—in less technical language, the
rope untwisted. This has been obviated by twisting alternate strands in oppo-
site directions, so that the tendency of part of the arm to untwist is counter-
acted by the counter movement of the other part, thus making the arm, as a
whole, perfectly rigid in rotating, while as perfectly flexible in lateral or
other directions of bodily movement."