Improvements in or relating to Variable Speed Gearing.
Year: 1899

page_text: Date of Application, 23rd Feb., 1899-Accepted, 3rd Feb., 1900
COMPLETE SPECIFICATION.
Improvements in or relating to Variable Speed Gearing.
We, THOMAS ALVA EDISON, of Orange, New Jersey, United States of America,
Scientist, and CHARLES M. JOHNSON, of Denmark House, Grove Hill Road, Redhill,
in the County of Surrey, England,. Mechanical 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 variable speed gearing its object being to provide an
improved construction and arrangement of gearing involving intercalated skeleton-
pulleys employed in combination with a specially-mounted adjusting-device to
form a variable speed gear without the use of a belt-tightening device and which
will preserve the alignment of the belt with the shafts.
This invention will now be described by reference to the accompanying draw-
ings of which
-
Figure 1 is a plan showing an arrangement of two skeleton pulleys to form a
variable speed gear:
Figure 2 a view showing in elevation the parts seen in Figure 1 together with
a method of tightening the belt: and
Figure 3 an end elevation of details of guide bearings for the controlling shaft.
Like letters indicate like parts through the drawings.
The two shafts to be geared together are shown at A and B, A being the driving
and B the driven shaft. Each shaft carries an expanding pulley formed of two
substantially conical members, the conicities of the two members of a pair being
opposed to one another; the two members of the pulley carried by the shaft A are
lettered C and D and those on the shaft B, E and F respectively.
In the example illustrated in the drawings each member is formed by a number
of bars which constitute the conical surface and the bars of the cone Care inter-
calated between those of the cone 1) their points of crossing forming substantially
a V-groove at the bottom of which the belt or band may lie.
Similarly the bars of the cones E and F are intercalated.
The cones are carried upon their respective shafts in such a manner that one
member of each pair is fixed thereupon and the other member capable of adjust-
ment by axial movement upon the shaft. The cones C and F are the adjustable
and the cones D and E the fixed members. The axial adjustments of the cones
and are in the example illustrated effected simultaneously in a manner herein-
after set forth, by means of links or arms connected to and operated by the rock-
shaft G in such a manner that the belt travels axially parallel to itself and remains
uniformly tight for all the obtainable velocity ratios of the shafts A and B.
As regards the details of construction of the pulleys shown in the drawings, each
set of ribs C, D, E and F is supported at its larger circumference by a conical
sheath, these sheaths being marked C, D, E, and respectively. The sheaths of
either pair forming a pulley serve, when the members forming that pulley are
advanced into proximity with one another to receive and cover the extremities of
the ribs at the smallest diameters, as well as to support and drive the extremities
at the largest diameters.

page_text: The extremities of the ribs of any set at the smaller diameter will for
simplicity be hereinafter termed the "inner," and those at the larger diameter, the
outer extremities.
"
The inner extremities of the ribs C are secured to a long sleeve C and the
small end of the sheath C is supported by a boss C, both the boss C² and
sleeve C being free to move axially upon the shaft A but either or both
being rotationally driven from the shaft, say by a feather, as indicated
at A. The sleeve terminates at C in a collar connected to the arms H in the
manner hereinafter described.
The inner ends of the bars 1) meet a' boss I3 which is 'keyed or otherwise fixed to
the shaft A, preferably by means of the key A', the sleeve C being slotted for
this purpose the outer ends of the bars Dare secured to the sheath D¹ whose
smaller end forms or is secured to the collar D2. The sleeve C³ can thus slide
axially within the collar De, rotational driving connection being provided between
them if desired by means of the feather A¹ or an equivalent device.
The cone C is thus driven from the shaft at the boss C and the sleeve C³
throuh the featherA' and the bars D through the boss D either alone or in con-
junction with driving connection at the collar D².
The pulley carried by the shaft B is similar in construction to that on the
shaft A except that, the cone E being fixed to the shaft B and the cone F being
adjustable axially upon the same, the inner ends of the bars forming the cone E
terminate in a boss fixed to the shaft B instead of in a movable sleeve as in the
case of the cone-and-the-cone-F which corresponds to-the-cone-D-is-capable-of
axial movement and is provided with a sleeve F free to slide upon the shaft B.
In mounting the pulley, comprising the cones C and D, upon. its shaft the
sleeve C is first placed thereon and the fixed member 1) is then secured to the
'shaft by any suitable means, such as by a screw or screws.
s passing through the
collar 12 or boss 1 and engaging with the key A' or with the shaft A itself; in
the latter case the sleeve C may be longitudinally slotted for a distance not less
than the maximum travel which it is desired to give to the movable cone C.
The movable member C is then placed upon the shaft, the free ends of its ribs
sliding in the spaces between the ribs of the fixed member. The free ends of the
movable member C are then attached to the sleeve C in any convenient manner,
such as by screws or the like; if desired the sleeve may be continued beyond the
ends of the ribs and be fixed to the sheath C¹ or boss C².
The adjusting device comprises the rock-shaft G operated by the hand-lever G¹
and carrying a movable sleeve H' and a fixed sleeve J¹. A feather H2 prevents
the shaft G from turning in the sleeve H. These sleeves carry respectively a
pair of arms H and a pair J. The arms H are pivotted to projections L' on a
sleeve L. The sleeve I can slide upon the shaft and the latter can rotate freely
within it; it also engages with the collar C+ so as to be capable of imparting axial
motion thereto without interfering with the rotation thereof.
This may be effected by ball or other bearings between the collar C and the
sleeve L or in any other well-known manner.
Similar connection is provided by a sleeve K K between the arms J and
the sleeve F2.
The shaft G is guided at each end by bearings M¹ and Q¹ respectively capable of
sliding in vertical guides, the weight of the shaft being taken by the two shafts A
and 13 from which it is suspended by the arms H, J.
The guide M for the bearing M¹ is pivotted at M² to any convenient support.
The whole shaft A is slung so as to be capable of swinging about the centre of
the shaft from which it is driven, preferably by toothed gearing as indicated in
dotted lines in Figure 2 at 01 and 0².
The operation of the device is as follows:-
The gear is shown in one extreme position in Figure 1, the pulley C D
being at its smallest and the pulley E F at its largest diameter.
The belting is indicated by the chain line P in the corresponding position.

page_text: If it is now desired to increase the velocity of the shaft B relatively to that
of A the lever Gi is moved over so as to make the cone C approach the cone D and
the cone Frecede from the cone E. The limiting positions of these movable
cones in this direction are shown in dotted lines in Figure 1.
The effect produced on the belt is to make it travel laterally with the movable
cones and parallel to its own plane of rotation and if it be a crossed belt it will
remain uniformly tight for all velocity ratios of A and B.
If it is desired to adjust the tightness of the belt this may be effected by
moving the shaft A about the centre of the driving shaft O. The shaft A is shown
in the drawings in its mid position the two extremes being indicated by dotted
circles in Figure 2 at A2 and A. This motion of the shaft. A causes the sleeve H
to slide axially along the shaft G and at the same time raises or lowers the
bearing M. The shaft G thus swings about the centre of the shaft B from which
it is slung by the arms J and the bearing at that end moves up or down in the
guide Q.
Any convenient form of mechanism may be provided for raising or lowering the
shaft A for the purpose of tightening the driving belt and the same mechanism
may also serve to hold the shaft A so that it is not drawn towards the shaft B.
This invention is not limited to the particular construction described above
by way of example as various modifications may be made without departing from
the spirit of the invention. The bars which form each cone although described
as solid with the other parts of the cone may be made detachable at either or both
ends, and if desired may be constructed of flexible or resilient material.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is:-
1. The combination with a variable speed gear comprising two pulleys of the
kind described of a shaft having movable bearings suspended from the two pulleys
by links which serve to adjust the pulleys to vary the speed.
2. The combination and arrangement of parts constituting the complete variable
speed gear substantially as described and illustrated in the accompanying
drawings.
L
1340
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