IMPROVEMENTS IN APPARATUS POR INDICATING AND REGULATING SPEED
Year: 1859

page_text: PROVISIONAL SPECIFICATION left by Edmund Hunt at the Office of
the Commissioners of Patents, with his Petition, on the 25th July
1859.
I, EDMUND HUNT, of Glasgow, in the County of Lanark, North Britain,
Consulting Engineer and Patent Agent, do hereby declare the nature of the
said Invention of "IMPROVEMENTS IN APPARATUS POR INDICATING AND REGULATING
SPEED," to be as follows, that is to say:-
This Invention has chiefly for object the indication of of the speed or rate of
moving details of machinery or of other moving bodies. It comprises a means
of measuring or indicating the ratio between two motions, and if one of the
motions is derived from or regulated by a clock or timekeeper, the indication
will give the rate of the other per minute or per other unit of time. Apparatus
embodying this part of the Invention consists of what may be termed a train
of gearing or its equivalent combined with automatic contrivances, by which
the ratio of the motion transmitted in either direction may be varied. The
opposite ends of the train are driven, one by each of the motions, to be
compared, and the intermediate parts become automatically adjusted so as to
cause the whole to rotate or move in unison. If any change occurs in either
motion, a new adjustment of the parts takes place, the position of details
connected with the adjustment always corresponding with and indicating the
ratio between the two motions. The adjustment is effected by a differential
movement arising from a change in the ratio between the two motions. This
part of the Invention is susceptible of embodiment in an innumerable variety

page_text: of mechanical arrangements, but in order that its nature may be clearly
understood, it may be stated that in one example of such arrangements a clock
is made to drive a cone, with which there is in contact a pulley on a screwed
shaft, the speed or rate to be indicated being imparted to this shaft. If the
rate has been regular for some time, the pulley and cone will be turning
harmoniously together, as if in gear, the screwed shaft turning synchronously
with the pulley. When the rate varies, there will be a differential movement
between the screw shaft and the pulley on it, which will cause the latter to
move longitudinally along the shaft and along the cone until it reaches a part
of the cone having a surface velocity the same as the altered surface velocity of
the pulley. The position of the pulley always corresponds with the ratio
between the clock motion and that to be indicated, so that an index connected
with the pulley will, on a suitable scale or dial, point out the rate per minute.
There may also be connected with the pulley or corresponding part a pencil,
which by tracing a line on a riband of paper or other surface moved regularly
under it by the clock, will produce a diagram recording the rate with all its
variations.
Instead of deriving what may be termed the standard or timekeeping
inotion of the speed indicator directly from a clock, it is preferred to derive it
from a separate source, and merely to regulate it by means of a clock. If the
entire power required were transmitted through the clock, the works would
have to be of extra strength, and no ordinary escapement would be suitable.
This Invention, however, provides for the use of an ordinary clock with a
spring or weight of ordinary proportion, a second or separate spring or weight
being employed for giving the extra power required. The action of the latter
is regulated by means of a worm driven by the clock; this worm being in
gear with a worm wheel turned by the second weight or spring. With this
arrangement the second spring or weight imparts no strain to the works of the
clock, and yet it cannot act more rapidly than the clock, by turning the worm,
will permit. The worm may be either helical or volute, the wheel in gear
with it being modified to correspond. The second spring or weight may be
made sufficiently powerful to keep the clock spring or weight constantly
wound up when suitably connected to it for that purpose. This method of
obtaining a regulated speed is obviously applicable to other apparatus besides
that for indicating speed.