IMPROVEMENTS IN DIFFERENTIAL WHEEL GEARING
Year: 1865

page_text: PROVISIONAL SPECIFICATION left by John Standfield at the Office of
the Commissioners of Patents, with his Petition, on the 17th March
1865.
I, JOHN STANDFIELD, of Thames Bank House, Pimlico, in the County of
Middlesex, Engineer, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN DIFFERENTIAL WHEEL GEARING," to be as follows:-
My Invention consists in certain novel arrangements and combinations of
wheels, and of parts connected therewith, forming a differential gear apparatus
which is applicable generally for transmitting motion, and for imparting either
increased or diminished power or speed to the machinery, apparatus, or parts
actuated by it. This improved differential gear is suitable for clockwork, for
screw cutting and wheel cutting tools, and other machines, for crabs, hoists,
and travelling cranes, for capstans, for steering apparatus of ships, and for
numerous other purposes, and I also intend to apply it as driving gear for my
improved governors, for which Letters Patent were granted to me, dated 27th
November 1861, No. 2979. The said gear in its usual form consists of four
spur wheels, which I will call a, b, c, & d, and of a driving wheel
or disc e, and the principal feature in my gear is that one of the spur
wheels is fixed and not revolving. The wheels a, d, and e are placed
on the shaft to which the apparatus to be driven is secured; a is loose on the
shaft, but secured to the framing or pedestal; d is keyed to the shaft,
and e, placed between a & d, revolves loose on the shaft. Through a boss
formed in the wheel or disc e passes a short arbor turning loosely in the boss;

page_text: to one end of this arbor is keyed the wheel 6 gearing into a, and to the other
end of the arbor is keyed the wheel c gearing into d. Supposing the wheels a
and c to be of the same diameter, and twice as large as the wheels b & d, it
follows that when the wheel has performed one revolution, the wheels b & c
will have passed once round the stationary wheel a and wheel d respectively
whilst the shaft with its appendages will have performed three revolutions. By
varying the sizes of the wheels the proportion of speed between the driving
wheel.e and the shaft can be varied at discretion according to the object to be
attained; thus when the differential gear is applied to a crab, or other apparatus
for raising and lowering heavy weights, the driving wheel may be made to
perform one hundred revolutions, or more or less, whilst the shaft with the
chain barrel attached will make but one revolution and gain power in proportion.
Owing to one of the spur wheels being fixed as described, and not revolving,
the gear has likewise the valuable property of remaining stationary, with a
weight suspended, when the driving wheel is let loose in a similar manner as
is the case in the well known differential pulleys, and which is of the greatest
importance in hoisting apparatus, in steering apparatus, capstans, and other
apparatus and machines, and also permits of the usual click or ratchet wheels
and palls being dispensed with. In some cases, for instance, when applied to
my patent governors, I connect the wheel, which I called a, with a weighted
lever, spring, or other contrivance instead of fixing it to the frame. When the
force applied exceeds the power to which the machine is set the weight will
be raised, or the spring or other contrivance will yield, and acting upon a
throttle valve or other apparatus will reduce the speed of or stop the machine
as the case may require. The driving wheel e may be a groove pulley, a strap
pulley, or it may be a toothed wheel driven through a wheel or pinion, or it
may have a handle fixed to it, and be driven by hand, or when applied to a
capstan it may be turned round by levers. Instead of toothed wheels the
grooved frictional wheels or pulleys may be employed. As already stated, my
improved differential gear and its modifications are applicable to a variety of
purposes in addition to those herein-before named.