Improvements in Variable Speed Gear.
Year: 1899

page_text: Date of Application, 23rd Mar., 1899
Complete Specification Left, 21st Dec., 1899-Accepted, 3rd Feb., 1900
Improvements in Variable Speed Gear.
I, WILLIAM HENRY NEWMAN, of Totteridge Park, in the County of Herts,
Engineer, do hereby declare the nature of this invention to be as follows:-
According to this invention a shaft is driven by a number (generally three) of
ratchet wheels or the like which are themselves intermittently and alternately
driven by an oscillating arm or arms, the extent of the oscillations and therefore
the speed of the driven shaft being varied at will.
In a convenient arrangement the driven shaft has fixed to it a toothed pinion
gearing with three toothed wheels placed round it at equal angles apart.
These wheels are themselves intermittently driven preferably by silent ratchets
and pawls through a three armed connecting rod from a variable throw crank on
a driving shaft in a line with the driven shaft.
I, WILLIAM HENRY NEWMAN, of Totteridge Park, in the County of Herts,
Engineer, 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:-
According to this invention a shaft is driven by a number (generally three) of
ratchet wheels or the like which are themselves intermittently and alternately
driven by an oscillating arm or arms, the extent of the oscillations and therefore
the speed of the driven shaft being varied at will.
Figure 1 is a transverse section, and Figure 2 a longitudinal section shewing
one convenient method of carrying out this invention.
Figures 3 and 4 are similar views of a modification.
Figures 5 and 6 shew a detail.
A is the driving shaft which may be driven by the prime mover in any
convenient manner.
B is the driven shaft which is connected to the machinery of which the speed
has to be varied.
The shafts A and B work in bearings C C which are in the same straight line
and which may be conveniently fixed in a frame or box D which forms an oil
chamber for the mechanism to work in.

page_text: On the end of the driving shaft A is fixed a variable eccentric E. This may
be conveniently made as shown. The shaft A is formed as a tube or sleeve and
has working in it a smaller shaft Fon the end of which is formed a small
eccentric. Surrounding this is the larger eccentric E and by revolving the one
eccentric inside the other by any suitable means, the throw of the combined eccen-
tric can be varied at will.
The sleeve A drives the eccentric E by means of the pin N on E which engages
in a slot in a collar which is formed on the end of A.
A convenient method of revolving the shaft F relatively to A and so altering
the throw of the eccentric is that shown in Figures 2, 5 and 6. A spiral slot A¹
is formed in the sleeve A and a straight slot in the shaft I the end of which
is made hollow and has a short rod F sliding in it. This rod has a pin F
through it at right angles which engages with both the spiral slot and the straight
slot. The end of the rod F is free to turn but not to move endwise in a bush F
carrying trunnions F5 free to turn in bearings in the hand lever F. If the
rod s is moved in or out of F by means of the hand lever F or other convenient
device the sleeve A and shaft F revolve relatively to one another.
Any other convenient method of altering the throw of the eccentric may be
employed.
A ring surrounds. the eccentric and preferably has between it and the
eccentric a row of balls or rollers in order to reduce the friction. This ring has
three blocks H H H which can slide round the edge of the ring but are retained
in a circular path by the ring being of the section shown.
The blocks H H H engage with pins or studs which are part of the three
ratchets or clutches J J J. These ratchets or clutches which are formed as part
of the three gear wheels L L L, and are preferably of the silent ratchet and
pawl type, work on three studs K K K which are fixed to the frame D.
The three gears wheels L L L all gear with the same pinion M which is fixed
to the shaft B and which they drive.
The action is as follows:-
-
When the eccentric has no radius or throw i.e. when its centre coincides with
that of the shaft A it simply revolves within the ring G. If however it is given
a small throw or radius, the blocks H H H which engage with the clutches J J J,
will reciprocate through a small distance and the clutches will revolve backwards
and forwards through a small angle, turning on the studs K K K.
The clutches will turn with them the gear wheels L L L but only in one
direction and as the clutches come into action alternately the shaft B will receive
a continuous rotary motion.
If the throw of the eccentric is increased, the angle through which the gear
wheels turn will be increased, and therefore the speed of B will be increased,
while reducing the throw will have the contrary effect.
By this means the speed of B can be varied from zero to the maximum for
which the mechanism is designed, the speed of A remaining constant.
The apparatus may also be arranged with the driving and driven shafts parallel
to one another instead of being in the same straight line.
In this case the driving shaft will have a number of variable eccentrics fixed
on it which will drive by means of rods or links a corresponding number of
ratchets. The speed of rotation of the driven shaft will then be varied as before
by varying the throw of the eccentrics.
Figure 3 is a transverse section, and Figure 4 a longitudinal section showing a
convenient method of carrying out this arrangement.
On the driving shaft a are fixed two variable eccentrics c c whose centres are
at right angles to one another.
On the driven shaft b are fixed two ratchet wheels or discs d d each of which
is driven by two ratchet arms which may be conveniently made in the form of
nipping levers, i.e. levers which nip and drive the wheel when moved in on⟫
direction but immediately release it when moved in the opposite direction.

page_text: Each eccentric is connected to the two ratchet levers on the corresponding
wheel on the driven shaft, by two rods or links. It will be seen that this arrange-
ment is equivalent to four eccentrics connected to single ratchets as in a single
revolution of an eccentric there are two driving strokes of the corresponding
ratchets.
The whole mechanism may be conveniently arranged in a box as before which
forms supports for the various parts and also an oil bath for them to work in.
In cases where it is necessary to reverse the motion and vary the speed in the
reverse direction, the apparatus would be combined with one of the usual forms
of reversing gear such as the three bevel wheels and clutches and so arranged
that the reversing gear would be thrown into action in the stop position of the
driven shaft, i.e. when the cranks have no throw. Then on starting the driven
shaft again its speed would be varied as before but in the reverse direction.
The apparatus may be combined with the usual differential gearing which is
employed in a vehicle to give the road wheels freedom of action in passing round
a curve.
A property of the apparatus which may be valuable in certain cases is that
the driven shaft can turn perfectly freely in its direction of rotation without
putting the driving shaft in motion.
Thus in the case of a vehicle running freely down a hill, the driven shaft,
which would be connected to the road wheels, would turn at a corresponding
speed, but it would not be necessary for the driving shaft or motor to be in
motion at all.
This property is due to the fact that the wheels which are driven by the
ratchets are quite free to overrun the ratchets in one direction.
Having now particularly described and, ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
1. The combination of a driving shaft, a driven shaft, two or more clutches
rotating the the driven shaft in one direction, an eccentric on the driving shaft,
a second eccentric surrounding the first, a strap on the second eccentric, connec-
tions between the strap and the clutches, and means for rotating the two
eccentrics relatively to each other.
2. The combination of a driving shaft, a driven shaft, three or more ratchet
wheels arranged at equal angles round the driven shaft, three or more toothed
wheels co-axial with the ratchet wheels and driven by them in one direction by
pawls, a toothed wheel fixed to the driven shaft and gearing with the other
wheels, an eccentric on the driving shaft, a second eccentric surrounding the
first, a strap on the second eccentric, connections between the strap and the three
or more ratchet wheels, and means for rotating the two eccentrics relatively to
each other.
3. Variable speed gear substantially as described and illustrated in the
drawings.