IMPROVE- MENTS IN PULLEYS GEARING WITH CHAINS AND IN DIFFERENTIAL PULLEY BLOCKS
Year: 1866

page_text: PROVISIONAL SPECIFICATION left by Henry William Ley at the Office of
the Commissioners of Patents, with his Petition, on the 21st March
1866..
I, HENRY WILLIAM LEY, of Bear Street, Leicester Square, in the County of
5 Middlesex, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN PULLEYS GEARING WITH CHAINS AND IN DIFFERENTIAL PULLEY BLOCKS," to
be as follows:-
The object is to obtain more effectually in practice that unlimited increase
of power which the differential pulley block offers in theory. Theoretically
the difference between the circumferences of the two pulleys (called hereafter.
A and B respectively) constituting the differential pulley block can be made.
less and less without limit, the power increasing as the difference diminishes,
that is as A and B become more nearly equal to each other.
Practically, however, since to prevent sliding a chain must be used for the
block and not a cord, the peripheries of the pulleys must be so constructed as
to engage with its links, and as no distinct engagement can be made for.
portions of a link taken separately the number of links engaged by A and B
must be whole numbers, and the difference between these numbers of links
(called D hereafter) must also therefore be a whole number. Indeed,, in the
differential pulley block as at present constructed D can never be less than 2
seeing that provision is made for the engagement of every pair of links only.
The first part of my Invention purposes reducing D to 1 by providing for the
distinct engagement by the peripheries of A and B of each link. Thus,

page_text: whereas by the present construction of A and B, if A engages 20 links, B
cannot engage more than 18, giving a power of 20 to 1, by my mode if A
engages 20 links, B can engage 19, and a power be acquired of 40 to 1.
Again, suppose a power of 160 to 1 were required, by the present construction
A and B must respectively engage 160 and 158 links, thereby so enormously
increasing the size of the block as to render it practically useless. Or else the
mechanical advantage of the block in itself must be left much less than 160
to 1 to keep it within reasonable size, and be brought up to 160 to 1 by
further mechanism extraneous as it were to the differential principal, which is
what is now. done. Even by my method of engaging the chain A and B must
respectively provide for 80 and 79 links, which though it would reduce the
apparatus to a much more manageable size than the numbers 160 and 158
would still leave it sufficiently cumbersome to be of little practical utility.
Some mode of obtaining a very great increase of power without the introduction
of complicated mechanism is therefore desirable, and this the second part of
my Invention proposes to furnish by so constructing the block that D need
no longer be confined even to 1 link, but can be in effect any the smallest
fractional part whatever of a link. Thus A and B might in effect respectively
engage 20 links, and 19, 192, 193, or be in effect still more nearly equal to
cach other, D would then become correspondingly, of a link or less,
find the power as 80, 160, 320, or more to 1. I adhere in my apparatus to
the principle of the differential pulley block, because among other things it
possesses with certain proportions (which can always be observed in practice,)
between its component parts the valuable peculiarity of not running down
when the load is left suspended, and as will be seen construct my block so that
though for convenience it may be worked otherwise, it always can be worked
by manual power directly applied to the chain itself.
My Invention then is as follows:-First, as to the distinct engagement of
each link of the chain; if a piece of ordinary oval link chain be passed round
á 'flat-faced pulley the position the chain will assume will be that in which
if a transverse section be made an end view of the chain after such section
would resemble a St. Andrew's cross, thus X, and if now the face of the pulley
be shaped to the chain each link will have a similar and separate engagement;
the kind of engagement that would result may be thus understood:-Suppose
the groove of a pulley to be primarily represented by three sides of a
regular pentagon. Let the outer sides be called the rims of the pulley, and
let the length of each side be equal to the breadth of the sectional X. Upon
the middle side as a base and between the outer sides construct a right
angled. triangle, the right angle to subtend the base; take away the base

page_text: and there will remain the representation of the groove of a pulley with
ridge between two furrows, and such that if a chain were passed over it, the
links would dispose themselves in accordance with the above sectional X, in
fact, would lie alternately on opposite sides of the ridge. It is with such a
groove that I form the snatch block of my differential pulley where engage-
ment of the links is not required.. On each side of the above ridge between
each two consecutive links on that side construct.projections extending each
into the link opposite to it on the other side of the ridge. Now fill in between
the rims (as above defined), and the chain at the intersection of each pair
of links. The links will then abut against the projections so formed on the
rims as well as the projections attached to the ridge, each link being engaged
separately from and similarly to another, this adaptation of periphery to chain
is applicable for wheels gearing with chains generally, and may be variously
modified to suit all cases where the links of a chain engaged with a
pulley lie otherwise than in the plane of circular section and perpendicular
to it.
Secondly, as to so constructing the block that D may be fractional; as now
made A and B which comprise the block are rigidly united. I do not unite
them rigidly, but attach them to each other by gearing, so that whilst both A
and B are revolving by means of the chain, one of them is slowly revolving in
the same or in the opposite direction by means of the gearing. This
can be effected by various combinations of spur, bevel, or other gearing.
The mode I at present prefer is to fix rigidly to one of the pulleys and on
the same axis a worm wheel, and to the other which rides loosely on the axis
to attach a worm so that it can work the worm wheel. The worm has fixed
on its axis a wheel, called hereafter C, the teeth of which are successively
moved by a fixed projection or projections or by a worm attached to the
pulley frame. Thus, suppose A and B engage equal (though this is not
essential) numbers of links, say 20; let the worm wheel have 20 teeth and be
moved through 1 tooth by 1, revolution of the worm; let C have 6 teeth, and
let there be a projection fixed to the pulley frame, such that C.moves through
one tooth each time that it comes in contact with the projection, that is each
revolution of the whole combination or block; now if an endless chain were
passed in the usual way over such a block, and if there were no projection to
catch the teeth of C, the block would revolve without any differential action
whatever; but as for each revolution of the block the projection moves C one
tooth the worm is moved one-sixth of a revolution and the worm wheel th
of a revolution; let the fraction of a revolution be in this case in the opposite
direction to that in which the block is revolving. For every revolution of

page_text: the block therefore A and B move relatively to each other through both of a
revolution, which is in effect the same as if one pulley periphery had 120
parts and the other 119; or as I have supposed 20 links as if one would
engage 20 and the other 19, a power would be thereby represented of 240
to 1, which could be increased to any extent without any further complication
(but with the mere provisión necessary for stronger chain) by increasing
the number of teeth of C; thus by making C 10 or 20, powers would be
respectively obtained of 400 and 800 to 1. If the moving of C by slight
jerks bé objectionable the worm before spokon of would afford continuous
motion. Of course in the above calculations friction has not been taken into
account.