Improvements in Pendulums for Tachometers.
Year: 1890

page_text: Date of Application, 15th July, 1890
Complete Specification Left. 7th Apr., 1891-Accepted, 9th May, 1891
PROVISIONAL SPECIFICATION.
Improvements in Pendulums for Tachometers.
I, THEODOR HORN of Leipzig, in the Kingdom of Saxony, Empire of
Germany, Doctor of Philosophy, do hereby declare the nature of this invention
to be as follows :-
The object of this invention is a pendulum for tachometers, in which the
oscillating bodies are attached to the ends of two leaf springs arranged parallel to
the axis of revolution, said springs being attached with their other ends to the shaft
and coming in contact by centrifugal force with two rails rigidly connected with the
shaft or with a prism placed thereon, and so bent as to determine the progress of,
and the maximal, centrifugal escape of the oscillating bodies.
By this arrangement, the deffection of the hand of the tachometer increases
approximately in proportion to the increase of rotary velocities.
The shaft is slotted and has a longitudinal groove in which slides a piston con-
nected by rods with the oscillating bodies. Through a connecting rod, the
movement of the piston is transmitted to a shaft having a peg or driver, by means
of which the movement is imparted to the shaft of the hand.
The degree of curvature of the above rails is so determined that those portions of
the springs, in which the momentum of bend is largest, are more and more supported
with the increase of rotary velocity. Thus the exactitude with which the hand
advances in proportion to the increase of axial speed depends greatly upon the
proper bend of the rails and the quality of the springs.
Dated this 15th day of July 1890.
A
وم
HUELSER & Co.,
Attorneys..
COMPLETE SPECIFICATION.
Improvements in Pendulums for Tachometers.
I, THEODOR HORN of Leipzig, in the Kingdom of Saxony, Empire of
Germany, Doctor of Philosophy, do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This invention relates to a tachometer in which the centrifugal force of rotating
oscillating bodies is employed as directing power for the hand.
Reference being had to the accompanying drawing,
Fig. 1 is a vertical section of the improved tachometer lodged in its casing, the
shaft with the oscillating body being shewn in front view.
Fig. 2 is a horizontal section through the middle.
Fig. 3 is a front view and
Fig. 4 a top view of the adjusting device, the casing being shewn as partly
broken through.
On the shaft A is mounted a prism P on which are screwed two leaf springs f
placed parallel to shaft A and carrying the two oscillatory bodies K K Figs.
and 2. With the increase of speed the oscillating bodies recede from the shaft,
until they occupy with the maximal speed the position K' K' Fig. 2. Shaft A is
slotted and has a longitudinal bore in which slides a piston K" connected by

page_text: rods ss with the oscillating bodies K. By means of connecting rode the move-
ment of the piston is transmitted to shaft W with driver R and from the latter to
the hand shaft *.
On the prism P are also secured two rails S S Fig. 2, on which bear the leaf
springs when bending through outwardly with increasing speed. If these rails S
were not provided the distance of the oscillating bodies K from the shaft would
increase in a greater proportion than the rotary velocity, as the bending through
of the springs is proportional to the centrifugal force, while the latter increases
in proportion to the product from the square of the angular speed and the
distance of the oscillating bodies from the shaft. In that case therefore the hand,
with uniformly increasing speed, would advance at first slowly and then more
rapidly and the above mentioned attaching, recommendable by its simplicity, of
the oscillating bodies direct to leaf springs lying parallel to the revolving shaft,
would be inapplicable for a practical instrument.
The rails S are so bent, that that supported point of the springs which lies next
to the oscillating bodies constantly advances towards the oscillating bodies and that
those points of the springs in which the momentum of bending is largest are more
and more supported with the increasing rotary velocity. Consequently the hand
can be made to advance in proportion to the increase of speed.
To allow a tachometer to be a proper indicator in any position of shaft A (lying
or upright) the position of the hand must be independent of the action of gravity
on the oscillating bodies and on the lever mechanism for the hand; it must be
dependent on the centrifugal force only.
The weight of piston K and rods and is compensated by counter poise G.
The action of gravity on the oscillating bodies K, if shaft A occupies horizontal
position, is transmitted by the rods s to piston K", which thereby undergoes a
pressure vertical to its direction of movement, therefore not influencing its position.
When shaft A occupies horizontal position the own weight of the oscillating
bodies acts approximately in the direction of the springs, therefore causing no
bending through of the same and consequently has little influence on the position of
the hand. When at a higher speed, the springs are perceptibly curved, also an
observable effect of the own weight of the oscillating bodies is produced on the
bending through of the springs which however (with sufficiently high numbers of
revolution) remains always small in proportion to the considerably increasing
centrifugal force.
With a mean rate of 1000 revolutions pr. minute and a distance of 1.8 centimetres
of the centre of gravity of the oscillating bodies from the revolving shaft, the
centrifugal force of the oscillating bodies would amount to twenty times their
weight. The component of gravity acting in the direction of the centrifugal force
would amount to about one tenth of the weight and consequently the influence of
the own weight of the oscillating bodies on the bending through of the springs
would be about one two-hundredth of the centrifugal force. By appropriate
selection of the counter poise G, the said inaccuracy of per cent., which in practice
would scarcely come into consideration, can be further compensated so as to become
totally imperceptible.
The hand shaft carries a glycerine damper consisting of a completely closed
hollow cylinder which is filled half with glycerine. The latter has by its inertia
and friction in the cylinder a damping effect on the movement of the hand without
impairing the susceptibility of the same.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :
A pendulum for tachometers, in which the oscillatory bodies are secured to the
ends of two leaf springs arranged parallel to the revolving shaft and attached.with

page_text: centrifugal force, on two rails S rigidly connected with the shaft and so curved
that that part of the springs which is supported by the rails, increases with the
increasing rotary speed, so that the deviation of the hand increases approximately
in proportion to the increase of velocity, substantially as illustrated and described.
D
A
1001
DR. THEODOR HORN.
By Huelser & Co.,
Temple Chambers, London, his Agents.