Year: 1896

page_text: SEBASTIAN ZIANI DE FERRANTI, of 27 Charterhouse Square in the County
of London, Engineer and Electrician, do hereby declare the nature of this invention
to be as follows:-
According to my invention I combine upon the same shaft a friction and toothed
wheel drive.
As is well known even where fine cut gear is used and allowed to run freely for
either multiplying or diminishing the speed of or transmitting power from one
shaft to another there is always a certain amount of knock on the teeth due to their
spring or shake in the gearing.
According to my invention I form a friction drive consisting of a plain wheel
upon each shaft and of exactly the same diameter as the pitch line of the teeth,
these two rollers I keep in easy contact by means of spring or elastic pressure, the
effect of this is that when each tooth has released from the work it is doing and the
next one comes into action there is no knock produced as is the case under ordinary
circumstances.
The friction drive transmits a certain amount of the power though not a large
amount of it with the result that the teeth are relieved from a small amount of
their work and come gradually instead of suddenly into gear.
The invention is specially applicable to perfect the running of cut teeth.
According to one method I carry it out by cutting away the sides of the teeth
of an ordinary pair of wheels and shrink or fasten a ring on to the shoulder so
formed and of the same external diameter as the pitch line of the teeth, the
driving and driven wheels may then be pressed together by means of a spring
contact, this always keeps the roller faces together and the teeth accurately to the
same depth, it also prevents any springing or knocking as above described.
According to another method where double helical cut wheels are used I cut
separately each side of the double helical wheel i.e. I make a wheel and cut it in
two parts to insert the roller wheel in the centre between the two sets of helical
teeth.
In some cases where a large slow running shaft is being driven or is driving
a small fast running shaft which is placed above it and a small fast running shaft
transmitting its power through a pulley or doing other work which would cause a
beavy drag on the bearings of the small shaft I relieve the bearings of the small
shaft of pressure by placing the large shaft in the direction of the pull and
providing both shafts with friction rollers bearing on each other. The bearings of
the large slow speed shaft thus take the strain which might otherwise interfere
with the running of the small high speed bearings.
I am fully aware that half shrouded teeth have been used in connection with the
wheels in which the teeth have been cast to size and left without machining; my
invention is not for this purpose which is the strengthening of the teeth and is not
applicable to teeth which are cast and left unmachined.
According to my invention the roller rings do not in any way strengthen the
teeth and are applied to wheels the teeth of which have been finally cut before

page_text: In some cases where wheels are held upon shafts and bracket as in the change
wheels and other gear wheels of a lathe it is sufficient for the purpose of carrying
out my invention to press the wheels together and the spring in the brackets and
other parts will keep the friction rolls in sufficient contact. My invention is
specially applicable to these change wheels and also for change wheels which are
used for driving and varying the gear on machine tools and other similar
appliances, a movable wheel may then be slid along a shaft and engaged in the
wheels of various sizes the friction discs alone adjust the depth of the teeth
besides taking up the backlash and knock and also keep the wheel or wheels in
position on the shaft as the friction discs control the sideways positions of the
wheels.
Dated this 11th dox of March 1000
Improvements in Toothed and Friction Gearing.
SEBASTIAN ZIANI DE FERRANTI, Hollinwood near Oldham, in the County of
Lancashire, late of 27 Charterhouse Square in the County of London, Electrician
and 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:-
My invention relates to improvements in toothed and friction gearing and has
for its object the reduction in the amount of shake on toothed gearing and the
increase of uniformity of motion where power is transmitted from one shaft to
another by means of toothed gearing.
As is well known even where fine gear is used and allowed to run freely for
transmitting power from one shaft to another whether the ratio of the gear be such
as to increase or decrease the number of revolutions, there is always a certain
amount of irregularity in the motion or knock with teeth due to spring, shake or
play in the gearing.
According to my invention I form a friction drive consisting of a plain wheel
upon each shaft of exactly the same diameter as the pitch line of the teeth and
I keep these wheels in contact by suitable means.
In order that my invention may be better understood I will now proceed to
describe it, having reference to the accompanying drawings on which the several
figures are marked with letters like letters having reference to the similar parts in
the several figures.
Figure 1. is a sectional elevation of a gear wheel and
Figure 2 illustrates two gear wheels in action.
In Figure 1. I show one means of carrying out my invention by cutting away
the sides of the teeth of an ordinary wheel and shrink or fasten on a ring, a, to the
shoulder formed by the cutting away the teeth at the sides of a gear wheel or
wheels. These rings, a, I make the same external diameter as the pitch line of the
teeth, the driving and driven wheels may then be pressed together, as shown in
Figure 2, by means of a spring, b. This always keeps the roller faces, a, together,
and the teeth accurately to the same depth, which also prevents any springing or
knocking as above described.
In Figures 3, 4, 5, and 6 I illustrate the application of my invention to helical
gears. Where double helical cut wheels are used I divide the wheel in two
parts, and insert in between these two sets of helical teeth the roller wheel, c.
In Figures 7 and 8 I show my invention employed where a large slow running

page_text: shaft, d, is driving or is being driven by a small fast running shaft, e, which is
placed above it and the small fast running shaft transmitting its power through a
pulley or being driven by a pulley 1 and belt m which would cause a heavy drag on
the bearings of the small shaft, e. I relieve the bearings of the small shaft, e, of
pressure by placing the large shaft in the direction of the pull and providing both
shafts with friction rollers ff, bearing on each other. The bearings of the large
slow running shaft thus takes the strain which might otherwise interfere with the
running of the small high speed bearings.
In some cases where wheels are held upon shafts and brackets as in the change
wheels and other gear-wheels of a lathe it is sufficient for the purposes of carrying
out my invention, to press the wheels together and the spring in the brackets and
other parts will keep the friction rolls in sufficient contact. My invention is
specially applicable to these change wheels and also for the change wheels which
are used for driving and varying the gear on machine tools and other similar
appliances and to further explain this part of my invention I illustrate in Figures 9
and 10 the application of my invention to change gear. The movable wheels i
may be slid along their shafts k and engage in the wheels of the various sizes. The
friction discs a are just the diameter of the pitch line of the teeth, and in addition
to taking up the back lash and knock also prevent the movement sideways of the
wheels when working owing to the pressure between the discs.
I am fully aware that half shrouded teeth are being used in connection with
wheels in which the teeth have been cast to size and left without machining, my
invention is not for this purpose, which is the strengthening of the teeth, and is not
applicable to teeth which are cast and left unmachined.
According to my invention the friction discs or roller rings do not in any way
strengthen the teeth and are applied to wheels the teeth of which have been finely
cut before using.
Having now particularly described the nature of my invention, and in what
manner the same is to be performed I declare that what I claim is :-
(1.) In tooth gearing in which the teeth of the wheels have been cut the
addition of friction wheels or discs of the same diameter as the pitch lines of the
teeth, substantially as described.
(2.) In toothed gearing the combination of toothed wheels having friction discs
or rollers of the same diameter as the pitch lines of the teeth with a spring to force
the discs into contact, substantially as described, in Figure 2.
(3.) In double helical toothed gearing, the forming of the wheel of two wheels
each with single helical teeth with the addition of a friction disc of the same
diameter as the pitch lines of the teeth, between the two wheels substantially as
described and illustrated in Figs. 3 4 5 & 6.
(4.) In combination, toothed gearing transmitting power from a fast to a slow
running shaft, a belt and belt pulley and friction rollers transferring the thrust due
to the pull on the belt to the slow running shaft. Substantially as described and
illustrated in Figs. 7 & 8.
(5.) In change gearing where cut toothed wheels are employed the use of
friction discs or rollers mounted on the wheels, of the same diameter as the pitch
lines of the teeth. Substantially as described and illustrated in Figs. 9 & 10.
Dated this 10th day of December 1896
S. Z. DE FERRANTI.