IMPROVEMENTS IN GEARING
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Fleeming Jenkin at the Office of the
Commissioners of Patents on the 19th September 1883.
85
FLEEMING JENKIN of 3 Great Stuart Street Edinburgh Civil Engineer
IMPROVEMENTS IN GEARING
"
The object of the present invention is to provide an improved mode of producing
and maintaining the pressure required between the different parts of gearing called
nest gearing in the Provisional Specification of the Patent granted to me N° 1913
in the present year.
I do this by an improvement in the second method of tightening there described
namely by the end motion of a cone. The improvement is effected by using a
roller coned at both ends and so constructed that a spring tends to force the two
cones asunder and jam or wedge them between two reverse cones in a rigid roller.
The inverse action by which a coned roller is pinched between two reverse cones
has already been described but the present arrangement has several important
advantages over that which first occurred to me.
For concentric nest gearing I form the expanding roller in two parts each coned
with the small part of the cone outermost. One part is fast on a pin and the
other part slides on this pin with a feather. A spring by preference a long spiral
steel spring forces the two parts asunder. When in the nest the cones are by this
spring pressed against rigid reverse conical surfaces-the wedging action causes the
necessary normal pressure between the rollers. With cones unless the surfaces are
curved as they may be for moderate pressures there will always be a slight
grinding action but by giving only a small draw to the cones this action will not
be found sensibly injurious. The reverse cones may be on a concave roller or on
one or more convex rollers. An expanding roller may be so placed that it bears
against reverse cones on two or more rollers. Or I can arrange the expanding
roller so that at one place its cones bear against reverse cones while at other places
the roller bears against a central cylindrical surface. There are numerous examples
in my Patent N° 1913 of arrangements in which the rollers are in this way divided
into concentric bands bearing against appropriate surfaces-expanding rollers can
be applied to these --the central band inay be larger than the cones equal to them
or smaller than they are.
I use a similar expanding roller applicable to right angle or oblique gearing-
the expanding roller is then one of the two called B and C in my previous Patent.
Those parts of the surface of B and C which bear against D and D, are either
rounded so as to bear on a small portion of their surface or suitably bevilled but

page_text: the surfaces of B and C which bear against one another are arranged as for a
concentric nest their axes being parallel. The wedging action of the expanding
roller inside the rigid roller forces the axes apart and jams the other surfaces
against D, and D.. This arrangement takes up the wear of right angled gear as
well as the spring described in my former Provisional Specification.
It has the further advantage of taking all end pressure off the axes whereas if,
as may be done the bands on each side of the bevil surface are flat and the rollers
are made solid some end pressure is required to give the jamming action. This
simpler arrangement is however useful. The above description applies to right
angled gearing the modification for oblique gearing is obvious.
Another mode of applying the expanding roller to a right angle nest is as
follows:-
Rollers made as before described bear against the inner concave surface of
rollers B and C which are turned so as to present two conical surfaces inside which
the jamming rollers act-while pressing at their other side against D, and D.. This
arrangement is also obviously applicable to rack nest gearing. Further I use the
expanding roller in this arrangement to give the normal pressure on the rack and
have a relieving spring placed as described in my provisional Specification N° 1913.
Or I may keep the old form of spring to produce the pressure and use the new
form of roller in the novel place now described with or without the special new
shapes of surface-this last arrangement diminishes the size of the pinching
nest D, D. and has special advantages even when the roller is not made to expand.
A similar arrangement is applicable to the sixth variety of nest gearing described
in my Provisional Specification N° 1913 called nest parallel gearing. An important,
form of this gear arises when a smooth pinion is pinched against the outer surface
of a smooth wheel by a right angle nest tightened by an expanding roller working
on the internal periphery of the wheel. Or the tightening expanding roller may
be outside. The several surfaces must then be of such diameters as will avoid all
grinding except that which is inevitable if the tightening cones are in contact for
any sensible length.
A simple frictional clutch is obtained by providing means for pinching the
expanding roller together-this tends to stop its rotation directly and allows the
surfaces to slip instead of roll-on releasing the roller the gear will be started
again.
These expanding rollers find applications which are obvious to the other forms of
nest gearing described in the above Provisional Specification. They tighten up the
gear without necessarily producing any end pressure on the bearings. They take
up the wear automatically they require no attention or skill in the attendant since
each roller is made with a spring sufficient to transmit the force for which the
gear is intended-the spring cannot be tampered with being wholly enclosed
in the roller the form of the spring is such that it gives a sensibly constant
pressure even after considerable wear has taken place the form is such that it is
easily constructed so that the surfaces shall be turned true and remain true under
the conditions of daily use they take up very little room and can be made
cheaply.
The expanding roller is also applicable to several forms of nest gearing as
described by Mess Ayrton & Perry in their Provisional Specification N° 3094 in
the present year.
Thus the expanding roller may form one of two placed between
an inner and outer concentric ring rigidly connected. In this case the expanding
roller is preferably placed next the outer ring which is doubly coned to receive it.