Improvements relating to Ratchet Wheels and Pawl Levers therefor.
Year: 1893

page_text: Date of Application, 17th Aug., 1893-Accepted, 14th Oct., 1893
COMPLETE SPECIFICATION.
Improvements relating to Ratchet Wheels and Pawl Levers
therefor.
I LAURITZ CHRISTIAN ANDERSEN, trading as Lauritz Andersen & Co. of Cort
Adelersgade 10 Copenhagen in the Kingdom of Denmark, Machinery Manufacturer,
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 combination of ratchet-wheel and pawl lever where by
oscillations of the latter the wheel can be actuated a greater or smaller number of
revolutions during a certain time.
On the usual concentrically arranged ratchet-wheels and levers this effect can
only be attained by moving the pawl over 1, 2, 3, 4 or more teeth at a time,
whereby velocities are attained proportional to 1: 2: 3: 4 and so on, but no inter-
mediate variations can be obtained.
On the eccentric ratchet-wheel and lever-combination which forms the object of
this invention, variations of speed can be obtained, lying between the above men-
tioned proportions and this in such great number, that, provided the wheel possesses
a sufficient number of teeth, it may be said, that practically the proportion of speed
may be varied without limits.
This invention is illustrated by the annexed drawing, in which the ratchet-
wheel A is excentrically arranged on the axis B, which latter has to actuate it
(Fig. 1 and 2). The excentricity being preferably 4th of the diameter, while the
pitch of the teeth is uniform all along the periphery, the angular movement, which
corresponds to one tooth at position a, will be about half as great as the angular
movement corresponding to a tooth at the opposite place at b. The arrangement
is preferably made so that the angle subtended at b is a little smaller than twice
the angle subtended at a. For the other teeth of the wheel the angle subtended
will receive a series of values, lying between these two extremes.
The spring pawl C is pivoted on the lever D, which oscillates on the axis B and
by means of a spring presses the pawl C against the teeth of the wheel. The lever
is supposed to be oscillated with certain uniform time intervals, while on the other
hand the angle of declination may be varied at will. Supposing, that the lever is
oscillated to such an extent, that the latch surpasses the teeth of the wheel for a
certain distance, the whole being greater than the length corresponding to the
angle subtended at b, but a little smaller than the length, which corresponds to
twice the angle subtended at a, the wheel, if for instance it possesses 100 teeth,
will always at 100 double oscillations of the rod complete one revolution.
If now the lever is adjusted so as to produce a little greater motion-say an
angular motion, which is very little greater than the angle subtended by a tooth
at 6-then the pawl at a moves forward two teeth t¹ and t² at the same time, while
on any other part of the wheel it only moves one tooth, as before. In this case
one revolution of the wheel is completed by 99 double oscillations of the lever.
The amplitude of movement of the lever being again increased a little, the pawl
advances also over the teeth t' and t² as well as t and t, so that consequently one
revolution of the wheel is performed by 98 double oscillations of the lever. A
further increase will require 97 double oscillations for each revolution of the wheel,
since in this case the teeth t¹ and t2, to and t' as well as to and to are operated as
pairs by the pawl, the remainder however singly. By thus gradually increasing
the amplitude of the pawl movement always an increasing number of the teeth
are overstepped as pairs by the pawl.

page_text: If the amplitude of movement of the lever D is increased, at certain places of the
wheel circumference 3 teeth at a time will be moved by the pawl, while at the
remaining places only 2 teeth at a time and lastly at the point 6 only one tooth at
a time; on further increasing of the amplitude also at the point b two teeth are
overstepped.
If the extent of movement of the oscillating lever is yet more increased, four
teeth at the point a will be moved at a time by the pawl, at the subsequent portions
of the periphery only 3 and finally at or about 6 only 2 teeth.
When the oscillating distance is still further increased 3 teeth will be overstepped
at a time by the pawl at the point b etc. In short a great number of variations of
speed is thus attainable by small degrees.
To prevent the wheel from going back, no pawl can be applied to the teeth
because the turning motion does not correspond to the division of the teeth, but to
attain the same purpose any friction-arrangement may be used, provided that it be
actually necessary to check return of the wheel.
Laterally to the wheel a disk E is provided, which is arranged so as to be
concentric with the axis and consequently also excentric to the wheel. This disk,
the circumference of which is smooth serves for the action of a frictional excentric
brake.
The desired effect may also be attained in another way. On the above described
arrangement the wheel is supposed to be excentric with regard to the axis to be
actuated, but the lever of the pawl concentric with the axis. However as the effect
only lies in the relative motion of the lever and the ratchet wheel, it is only
necessary, that the lever be to an appropriate degree excentrically arranged with
regard to the ratchet-wheel, without regard to, whether the wheel is placed
concentrically or excentrically to the axis because in any case the number of
revolutions of the wheel and the axle on which it is fixed, will remain the
same.
The apparatus may consequently be modified by placing the wheel concentrically
and the lever excentrically or by both wheel and lever being placed excentrically
on the axis.
In Figs. 3 and 4 an arrangement of the first kind is shown in lateral view and
section, that is to say, the wheel is here placed concentrically and the lever
excentrically on the axle. The axle B possesses an excentric thickening, on which
the wheel A is arranged, the central boss of the latter being excentrically bored
out, so as to have the same excentricity as the thickened portion of the axle. The
wheel is thus concentrically arranged with the axle and fixed on the same, for
instance by means of a small screw.
The hub of the pawl lever surrounds the excentric thickening, so that the lever
oscillates excentrically on the wheel A. and the axle B. The friction-disk may as
before be made of one piece with the wheel.
Figs. 5 and 6 illustrate an instance, where the wheel and the lever are both
arranged excentrically. This arrangement is substantially the same as that in
Figs. 3 and 4, only the bore of the wheel is more excentric than the enlarged part
of the axle, so that the wheel-if it is arranged, as shown in the fig., will lie with
its centre for instance at the one side of the centre of axle B, just as far distant
from the axis as the centre of rotation of the lever, which latter is of course also
the centre of the enlarged part of the axle, lies to the other side of the centre of
the latter.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
An improved combination of ratchet-wheel and pawl lever in which the ratchet
wheel A and lever D rotate on different axial centres, for the purpose of attaining
an increased number of possible variations and more minute capacity of variation

page_text: in the relative proportions of number of revolutions of the ratchet-wheel and
oscillations of the lever on altering the amplitude of the said oscillations; sub-
stantially in the manner herein described.
Dated this 17th day of August 1893.
R. HADDAN,
Herbert Haddan & Co.,
18, Buckingham Street, Strand, London, Agent for Applicant.