Improvements in Frictional Driving Gear for Shafts at a Right or other Angle to each other.
Year: 1895

page_text: Date of Application, 18th June, 1895-Accepted, 3rd Aug.,
1895
COMPLETE SPECIFICATION.
Improvements in Frictional Driving Gear for Shafts at a Right or
other Angle to each other.
I, CHRISTIAN SEYBOLD, of Zweibrücken, Germany, 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:
This invention relates to the method of transmitting motion, whereby motion is
imparted from one friction wheel to another through a frictional belt situated
between the two frictional surfaces of the wheels, by shifting this belt between the
wheels the ratio of transmission can be varied.
This method of transmission has hitherto only been applied by means of coned
wheels whose axes are parallel to each other and the smaller ends of which lie in
opposite directions.
It has been attempted to apply this method to pullies the axes of which are not
parallel, but without success, as it has not been possible up to the present time to
construct frictional gear in which the frictional belt situated between the coued
surfaces of the wheels on shafts at an angle to each other, did not follow the known
law whereby the belt tends to shift laterally from its correct position towards the
larger diameter of the driving wheel, or in other words no construction has been
arrived at in which the belt was self-guiding.
In order to render the friction belt between the coned surfaces self guiding for
shafts at an angle to each other, it was proposed to make the hollow conical wheel
with a slightly convex surface, and the full conical wheel with a slightly concave
surface. But even then no useful transmission can be obtained unless the following
details of construction, which form the subject of my present invention, are
observed, as with these alone can a useful variable ratio of transmission be obtained
with friction wheels on shafts placed at an angle to each other.
I will describe my said improvements with reference to the accompanying
drawings in which Fig. 1 shows a perspective view of the improved frictional
driving gear, Fig. 2 shews a front view, Fig. 3 a side view, Fig. 4 a plan, Fig. 5 a
side view with some of the parts omitted, Fig. 6 a detail of Fig. 4, and Fig. 7
diagram view of the frictional wheels.
The same parts are designated by the same letters in each of the figures.
The improved construction is more particularly applicable in all those cases in
which a shaft is required to drive a number of other shafts all situated at a right
or other angle thereto, whose speed is required to be separately adjustable, and
which require to be thrown out of gear either separately or simultaneously; but it
is equally applicable for transmitting motion to a single shaft at an angle.
A is the driving shaft which is to impart motion to one or more shafts B.
The shaft B is carried in a bearing at C which can be shifted in an axial
direction, and carries the friction wheel D which receives motion from the friction
wheel E on A through the medium of the belt F.
The friction wheel D is pressed by a weight G against the friction wheel E, this
being effected in the example shown, by means of a lever R turning on a fixed
pin and gearing by means of a toothed quadrant S with teeth T or a worm wheel
on the underside of the shiftable bearing C.

page_text: The pressing of the wheel D against the wheel E can of course be effected in a
variety of ways by means of weights or springs, with or without the use of levers.
By raising the weight G or lever R, the frictional pressure between D and E
can be stopped, and consequently the rotation of shaft B be arrested.
The shifting of the friction belt F between the two friction wheels, is effected by
the belt guide U.
In practical trials with such frictional gear it has been found that the friction
belt F must embrace so much of the smaller wheel E that the belt F will be carried
along thereby even when the friction wheel D is stationary, that is to say, when
the latter is thrown out of gear by raising the weight G or lever R. This is
necessary because, both when thrown out of gear and also when the driven wheel D
is put in gear, the belt F would be scoured through at one point by the frictional
action of the driving wheel E if it were stationary.
The slightest wear of the belt at one point by scouring would give rise to an
irregular transmission of motion resulting in a rapid wear of the belt F. On this
account the guide rollers M M of the belt, as shown at Figs. 1, 3, 4 and 5 are so
placed that the portion of the belt which passes to the point of frictional contact
rous in an obtuse angular path while the other part of the belt runs in a straight
path.
The necessity of causing the belt F to partially embrace the driving wheel E
determines a certain relation between the size of the driving wheel E and that of
the driven one D. This proportion must not be smaller than 1 to 3, as otherwise
the disadvantage arises that the surfaces of the driving cones E and D become too
steep, the result of which would be that the friction belt F when sufficiently
embracing the driving wheel E, would have a tendency notwithstanding the concave
and convex forms of the conical surfaces, to run towards the higher edge or larger
diameter of the wheel E.
In order that the friction belt F, in the disengaged condition of the gear, shall
always be carried along by the wheel E with certainty it is also necessary, in
addition to the former properly embracing the latter, and to the proper proportions
of D and E, that the belt F shall always have a uniform tension imparted to it.
This tension of the belt is also necessary for the gearing when engaged, and must
be produced automatically as the belt F becomes stretched like every other belt,
such stretching being increased by the pressure exercised by the wheels D and E
upon the belt. For the above purpose the lower guide roller M of the friction
belt F is arranged, as shewn at Figs. 1, 2 and 3, in a fork I freely shiftable down-
wards, and by means of springs, weights, or weighted levers O acting on this freely
moveable roller M', a very uniform tension is always maintained in the belt.
Furthermore it has been found that it is of advantage that the guide rollers M M'
should not both lie in the direction of the contact surfaces of the friction wheels or
rather that neither of them should lie with its periphery exactly in the direction of
the line of contact of the wheels D and E, but rather that either only the upper
guide roller M should be adjusted to this position, while the lower roller M' has its
axis in a twisted position relatively to that of M, or the axis of the upper roller M
is also not parallel to the line of contact of the wheels, while the two axes of both
the guide rollers M M¹ are at an angle to each other, as shewn at Fig. 4.
This peculiar position of the guide rollers M M' is determined by the fact that
the friction belt F is bent by the driving wheel E somewhat more at the higher
edge thereof than at the lower edge, whereby the belt F is made to assume a form
which requires to be compensated for by the above described position of the guide
rollers M M in order to produce a uniform tension in the whole width of the belt,
and to keep this in a self guiding condition.
The most advantageous position of the guide rollers M M is best obtained by
carrying the upper guide roller M in an adjustable support J as at Figs. 1, 2 and 3
which on trial is adjusted to and fixed in the position in which the belt F shows no
tendency to shift laterally, while the lower guide roller M' is carried in a fork 1

page_text: which can turn at will laterally to any extent as shewn at Figs. 1, 2, 3 and 6,
whereby the roller M' is made to freely follow the form of the belt F in any
desirable position to which it is adjusted.
In the course of my experiments I also found it of advantage to make the guide
rollers M M for the friction belt F either of a width corresponding to the frictional
surfaces of the friction wheels E D, or to make them narrow and with freedom to
shift laterally, as the friction belt F, in being shifted laterally between the friction
wheels E D, will of itself shift laterally on the wide guide rollers, or will cause the
narrow shiftable guide rollers to follow its lateral motion.
Lastly in order to satisfy the condition that the friction belt must have absolutely
the same speed at its two opposite edges or at any two points of its surface that are
at equal distances from the centre line of the belt in the transverse direction, if it
is to be really self guiding, that is to say, if it is to have no inherent tendency to
shift laterally between the wheels (which is entirely dependent upon the correct
relative proportions of the diameters of the wheels I ) it is necessary that the
wheels DE shall have diameters of a perfectly definite size, as shewn in the
diagram at Fig. 7, namely that the diameters of the end surfaces of the full conical
wheel (driving wheel E) and those of the hollow cone (driven wheel D) shall have
a definite ratio. Referring to Fig. 7, the diameter of the end surface a-b must be
to the diameter of the surface c-d of the wheel E as the diameter of the
surface e f is to the diameter of the surface g-h of the wheel D, or in other
words, the diameters a-b and e-f of the two wheels must be in the same
proportion as the diameters c-d and g-h thereof.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In frictional driving gear consisting of a full and a hollow conical wheel of
which the first one has a concave and the second one a convex surface with variable
ratio of transmission for shafts at right or other angles to each other, and operating
in combination with a frictional belt travelling between the two frictional surfaces
that are pressed towards each other, the arrangement of the guide rollers of the
frictional belt in such manner, that the belt is made to embrace the driving wheel
to such an extent that this will always carry the belt along even when the driven
wheel is out of contact, substantially as described.
2. In frictional gear of the kind referred to in the first claim, so constructing the
two wheels that the proportion between the diameters of the driving wheel and the
driven wheel shall not be less than 1 to 3, as with smaller proportions the cone
surfaces of the frictional discs would be too steep so that with a sufficient extent of
frictional contact between the belt and the driving wheel the belt would tend to
shift towards the larger diameter of the latter, notwithstanding the correct
formation of the concave and convex frictional surfaces of the wheels, substantially
as described.
3. In frictional gear of the kind referred to in the first claim, arranging the
upper guide roller of the friction belt so that it can be adjusted in any desired
position, substantially as described.
4. In frictional gear of the kind referred to in the first claim, arranging the
lower guide pulley of the friction belt so that it is free to move both laterally and
in the longitudinal direction of the belt, and is subject to a pull by a weight,
spring or weighted lever in such manner as to produce a uniform tension of the
belt, substantially as described.
5. In frictional gear such as is referred to in the first claim, constructing the
guide rollers for the friction belt either of suitable width for allowing the belt to
shift thereon when it is adjusted laterally, or so as to be free to shift laterally with
the belt when this is adjusted, substantially as described.
6. In frictional gear such as is referred to in the first claim, proportioning the

page_text: diameters of the wheels in the manner herein described, so that the frictional
surfaces thereof shall have the correct concave and convex form and the friction
belt shall have no tendency to shift laterally.
Dated this 18th day of June 1895.
ABEL & IMRAY,
Agents for the Applicant.