Improvements in Differential Pulleys.
Year: 1895

page_text: Date of Application, 30th Apr., 1895
Complete Specification Left, 30th Jan., 1896-Accepted, 7th Mar., 1896
Improvements in Differential Pulleys.
A communication from abroad by THOMAS ALDRIDGE WESTON, of Rock Hall,
Township of Arden, North Carolina, United States of America, Engineer.
I, JOHN CLAYTON MEWBURN of the Firm of J. C. Mewburn and Ellis of
55 and 56 Chancery Lane in the County of London, Chartered Patent Agents, do
hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in pulleys applicable for raising weights,
actuating presses, and for other like purposes. According to this invention the
improved pulley may be constructed in the following manner :-
In a pulley block frame, two separate toothed or pocketed chain sheaves, of
differential or of equal diameters, are mounted upon suitable axles; and engaging
with the teeth of the said two sheaves is an endless lifting or load chain, pendent
therefrom in two loops. In one loop is placed an ordinary snatch block, whereby
to attach a load. One of the aforesaid sheaves is for hoisting only; the other
only for lowering. Integral with the hoisting sheave, is a spur toothed flange, or
spur wheel, engaged with the spur pinion of a driving shaft. The said toothed
flange is checked against backward rotation by differential pawls pivoted to
the frame. The lowering sheave is provided upon one side with the disc brake
described in the Specification of Letters Patent dated 29 January 1863 No. 263
whereby the said sheave may have a frictional abutment against the frame; and its
other side is provided with the frictional incline device described in the Specifi-
cation of Letters Patent dated 6 June 1868 No. 1867 whereby the said disc brake is
operated, to retain and lower the load. One of the said inclines is formed centrally
upon a light spur wheel or lowering wheel; the corresponding incline being
formed upon the adjacent boss of the lowering sheave. The lowering wheel
engages with a pinion placed loosely upon the driving shaft. The said pinion is
provided with a sleeve whereon is fixed a ratchet wheel. Another ratchet wheel
is fixed to the outer end of the driving shaft; the teeth of the said two ratchet
Between the said ratchet wheels,
wheels being respectively right and left hand.
and loose upon the driving shaft, is the driving sprocket wheel provided with the
usual hand chain, and also with two pawls engaging with the two ratchet wheels
one on either side of the said sprocket driving wheel. Upon rotating the driving
sprocket wheel in one direction, the ratchet wheel fixed to the driving shaft is
rotated with its affixed pinion, and thereby also the engaged spur wheel and hoisting
sheave thus raising the load. Upon ceasing such motion, the differential pawls
arrest backward motion, and retain the load. Reversing the rotary motion of the
sprocket driving wheel, leaves the driving shaft at rest along with the hoisting
sheave but rotates the lowering ratchet wheel and its pinion, loose upon the driving
shaft; thereby rotating the spur lowering wheel and its attached incline, the other
incline upon the lowering sheave following with its sheave; the load then
descending so long as this reverse motion is maintained. Upon ceasing the latter
the load remains suspended, by the action of the inclines and discs, as set forth
in the Specification of the aforesaid Letters Patent of June 6th 1868 No. 1867.
The spur gearing of the hoisting sheave has its velocity ratio proportioned to
the load capacity of the machine, for example, so that one man may easily raise the
full load whereas the spur gearing of the lowering sheave is made of a different

page_text: velocity ratio, ɛo as to effect a very rapid lowering of the load. The said
differential speeds of the hoisting and lowering motions each one operated by the
appropriate reverse motion of the driving sprocket wheel, form one object of the
invention for the saving of time, effort and wear in such mechanism. The inven-
tion also affords two differential speeds of hoisting viz. :-the one already referred
to, effected by the spur gearing and driving shaft; also another and more rapid
upward motion at a speed of two to one by simply hauling upon the slack load
chain depending from the hoisting sheave.
According to this invention the unvarying movement of the endless load chain
is compelled in one direction, both in hoisting and in lowering, due to the said
chain hanging from opposite sides of the two load sheaves one of which is only
capable of taking up chain, to hoist; and the other only capable of paying it out
to lower. Should the apparatus therefore be employed for exclusive hoisting or
exclusively for lowering loads, in either case, the endless load chain circulates only
in one and the same direction, unaffected also whether the heights of such lifting
or lowering be short, long, or variable; thus securing perfect uniformity in the
wear of the chain.
Dated this 30th day of Amil 100%
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.
A communication from abroad by THOMAS ALDRIDGE WESTON, of Rock Hall,
Township of Arden, North Carolina, United States of America, Engineer.
I, JOHN CLAYTON MEWBURN of the Firm of J. C. Mewburn and Ellis of
55 and 56 Chancery Lane in the County of London, Chartered Patent Agents,
do hereby declare the nature of the said 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 improvements in differential pulleys applicable for
raising weights, actuating presses, and for other like purposes. According to this
invention the improved pulley is constructed in the following manner :-
In a pulley block frame, two separate toothed or pocketed chain sheaves,
of differential or of equal diameters, are mounted upon suitable axles; and
engaging with the teeth of the said two sheaves is an endless lifting or
load chain, pendent therefrom in two loops. In one loop is placed an ordinary
snatch block, whereby to attach a load. One of the aforesaid sheaves is
for hoisting only; the other only for lowering. Integral with the hoisting
sheave is a spur toothed flange or spur wheel, engaged with the spur pinion
of a driving shaft. The said toothed flange is checked against backward
rotation by differential pawls pivotted to the frame. The lowering sheave is
provided upon one side with the disc brake described in the Specification of
Letters Patent dated 29 January 1863 No. 263 whereby the said sheave may have
a frictional abutment against the frame and its other side is provided with the
frictional incline device described in the Specification of Letters Patent dated
6 June 1868 No. 1867 whereby the said disc brake is oper ted to retain and lower
the load. One of the said inclines is formed centrally upon a light pur wheel or
lowering wheel; the corresponding incline being formed upon the adjacent boss of
the lowering sheave. The lowering wheel engages with a pinion placed loosely
upon the driving shaft. The said pinion is provided with a sleeve whereon is fixed
a ratchet wheel. Another ratchet wheel is fixed to the outer end of the driving
:

page_text: shaft; the teeth of the said two ratchet wheels being respectively right and left
hand. Between the said ratchet wheels, and loose upon the driving shaft, is the
driving sprocket wheel provided with the usual hand chain, and also with two
pawls engaging with the two ratchet wheels one on either side of the said sprocket
driving wheel. Upon rotating the driving sprocket wheel in one direction, the
ratchet wheel fixed to the driving shaft is rotated with its affixed pinion, and
thereby also the engaged spur wheel and hoisting sheave, thus raising the load.
Upon ceasing such motion, the differential pawls arrest backward motion and
retain the load. Reversing the rotary motion of the sprocket driving wheel
leaves the driving shaft at rest, along with the hoisting sheave, but rotates the
lowering ratchet wheel and its pinion, loose upon the driving shaft; thereby rotating
the spur lowering wheel and its attached incline, the other incline upon the lowering
sheave following with its sheave; the load then descending so long as this reverse
motion is maintained. Upon ceasing the latter, the load remains suspended, by the
action of the inclines and discs as set forth in the Specification of the aforesaid
Letters Patent of June 6th 1868, No. 1867.
The spur gearing of the hoisting sheave has its velocity ratio proportioned to
the load capacity of the machine,-for example so that one man may easily raise the
full load, whereas the spur gearing of the lowering sheave is made of a different
velocity ratio, so as to effect a very rapid lowering of the load. The said
differential speeds of the hoisting and lowering motions, each one operated by the
appropriate reverse motion of the driving sprocket wheel, form one object of the
invention for the saving of time, effort and wear in such mechanism. The invention
also affords two differential speeds of hoisting, namely the one already referred to,
effected by the spur gearing and driving shaft; also another and more rapid
upward motion at a speed of 2 to 1, by simply hauling upon the slack load chain
depending from the hoisting sheave.
According to this invention, the unvarying movement of the endless load chain
is compelled in one direction, both in hoisting and in lowering, due to the sai
chain hanging from opposite sides of the two load sheaves one of which is only
capable of taking up chain, to hoist, and the other only capable of paying it out,
to lower. Should the apparatus therefore be employed for exclusive hoisting or
exclusively for lowering loads, in either case, the endless load chain circulates only
in one and the same direction; unaffected also whether the heights of such lifting
or lowering be short, long or variable, thus securing perfect uniformity in the wear
of the chain.
Having stated the nature of the invention, I will now describe it more particularly
with the aid of the annexed illustrative drawings.
Figure 1 is a sectional side elevation of the new differential pulley, through the
line 2-2 of Figure 2, the chain which is of the usual form for chain blocks
being omitted; its location however is obvious by that of the chain sheaves; the
path or course of the load chain is shown by Figure 4 and is in this example
similar to that of Weston's well known differential pulley described in the
Specification of Letters Patent dated April 25, 1859, No. 1033.
Figure 2 is an end elevation with the pawl details sectional on the line 3-3 of
Figure 1.
Figure 3 is a partial transverse sectional view on the line 1-1 of Figure 1.
A A A² are frame plates united by three stays X X X2, their screwed ends
being threaded as at X³ into the plate A; their other ends are screw-nutted into
the plate A' as shown at X'. B'is a cross-head further uniting the frame plates
and provided with the usual book B. C is the hoisting sheave and D is a spur
wheel, both made integral with the shaft D¹ by means of keys C, D³. E is the
lowering sheave loose upon a stay or axle F, the latter having its end F' screwed
into the boss A³, and its other end screw-nutted to the plate A'. The sheaves C
and E, which are also shown diagrammatically in Figure 4, engage with an endless
chain in the usual manner, applied thereto in two loops as represented in Figure 4.
In one loop N is a common snatch block G for attaching the load.

page_text: The lowering sheave E has a boss E' carrying the friction discs E' and engaged
to them by key projections E³. Alternating with the discs E² are stationary discs
or friction plates H, engaging by lugs H¹ with the side stays X'X², Figures 2
and 3. The sheave E has also a helical faced boss E, coacting with the helical
faced boss of the lowering wheel I. The said wheel I has also a boss 12 5
having frictional coaction with and abutment against the frame boss A+. The
wheel I engages with the pinion K. The latter has a sleeve extension K passing
through the frame boss or bearing A³ and screw threaded to a right hand toothed
ratchet wheel K similar to M2, but having reversed teeth and capable of being
driven by the pawl K³ pivotted upon the inner face of the driving sheave L. 1
M is a pawl likewise pivotted to the sheave L for driving the left hand toothed
ratchet wheel M2, the latter being screwed and pinned to the outer end of the
shaft M. The other end of the shaft M is integral with the pinion M³ engaged
with the spur wheel D. The latter is checked against backward motion by
pawls D D pivotted on the outer ends of the stays XX. The pawls D³ D
are held to the teeth of the wheel D by an internal spring, such as shown within the
pawls K³ and M. The construction and advantages of this form of pawl are
more fully set forth in connection with Figures 12 to 16 of the Specification of
Letters Patent No. 1196 dated April 27, 1866. The frictional inclines E' and I'
are those described in Specification of Letters Patent dated June 6, 1868 No. 1867
and the friction dises E2 Hare those described in the Specification of Letters
Patent dated January 29, 1863 No. 263.
The operation of the pulley is as follows:-
The endless load chain being applied to the sheaves C and E as shown in the
diagram Figure 4, and a load being placed upon the snatch block G, the said load
may be thus raised and lowered. Force being applied to the endless band chain
of the sheave L to rotate the latter in a left hand direction, such motion will be
imparted by the pawl M₁ to the ratchet wheel M², shaft M, pinion M³, wheel D,
shaft D and sheave C, thus picking up chain from the loaded loop O, Figure 4,
over the distant side of the sheave C in Figure 1, and raising the load. Upon
ceasing such left-hand driving motion in the sheave L, the reaction of the load
takes effect through the teeth of the wheel D upon one or other of the pawls D³ D'
When commencing the
which prevent all reverse motion in the said wheel D.
said hoisting motion and so soon as the strain of the load comes upon the snatch
block G and loop N, Figure 4, one half of the strain is then upon the side of
the said loop pendent from the sheave E causing the said shield to yield and turn
slightly in the direction of the arrow thereon, thus causing its incline E* to climb
or mount slightly the incline I' of the wheel 1, the latter being held stationary by
the retarding friction of its boss 12 against the contiguous part of the frame A².
The said climbing of the inclines yields a proportionate axial thrust of the sheave
Hange E' upon the discs E2 and H compressing them against the frame A' and
arresting all further motion when the resultant disc friction has become sufficient.
The suspended load therefore thus always provides itself with sufficient brake
action to hold it at rest, and no more. Upon reversing the motion of the sheave L
to a right hand one, the hoisting mechanism being then at rest, the pawl K³ rotates
the right hand toothed ratchet wheel K2, its attached pinion K and wheel I in the
direction to make the incline 1' descend the incline E. At the first instant of
such reversed motion, the load retaining friction of the discs E2 and H being
reduced, the sheave E yields to the pull of the load in a direction to make its
incline E again ascend the incline I and restore the sustaining friction, the
incline E closely following the said lowering motion of the wheel I so long as
continued and ceasing with it. It is obvious that the axial thrusting action of the
inclines from each other under a load has its reactions between the frame
plates A A³, thus utilizing the said stationary parts for brake purposes.
In a fixed hoist, wherein bulk is allowable, the discs E' and H may be fewer
or be wholly omitted, sufficient brake surface being obtained by increase of diameter
in the discs or by direct friction of the flange E³ upon the single friction surface

page_text: of the frame plate A¹. In such case however the thrust of the inclines becomes
greater and the reactions more severe upon the frame.
With the proportions shown in the gearing and sheaves, the hoisting speed is
about 28 to 1, and the lowering speed about 7 to 1.
The said differential velocity
ratios respectively for hoisting and lowering effect an obvious saving of time, labor
and wear in hoisting and lowering loads; an the constant circulation of the load
chain in one and the same direction effects like economy in the wear of the said
chain by diffusing the wear equally throughout its length.
Having now particularly described and ascertained the nature of the said inven-
tion as communicated to me and in what manner the same is to be performed I
declare that what I claim in respect of differential pulleys is :-
1. The combination of two independent load sheaves, one for hoisting, one for
lowering, and an endless load chain thereon, a common driving shaft, and suitable
gearing whereby both of the said load sheaves are respectively operated, substan-
tially as hereinbefore described.
2. The combination of an endless load chain capable of being moved or circulated
in one direction only by means of the operating gear and its one driving shaft,
and a hoisting or load sheave and a lowering sheave capable of receiving a
lowering motion only from the one operating shaft, and the said operating shaft
and gearing capable of operating alternately either of the said two sheaves for
alternate hoisting and lowering, each at different velocity ratios, substantially as
hereinbefore described.
3. In a differential pulley having separate hoisting and lowering sheaves, and an
endless load chain thereon, and a common driver for both sheaves, a lowering
sheave constructed for coacting on one of its sides with a frictional incline
lowering wheel and on its other side with a friction brake, substantially as
hereinbefore described.
4. In a differential pulley having separate hoisting and lowering sheaves and an
endless load chain thereon and a common driver for both sheaves, a lowering
sheave constructed for coacting on one of its sides with a frictional incline lowering
wheel and on its other side with a friction brake, the said frictional parts each
having their frictional connection with and reactions upon adjacent stationary
parts integral with the frame of the machine, substantially as hereinbefore
described.
5. In a differential pulley having separate hoisting and lowering gear both
operated by one common driving shaft, a sprocket driving sheave or equivalent
rotatory driver provided with ratchet devices thereon whereby the said driving
shaft and a pinion loose thereon can each be alternately driven, substantially as
hereinbefore described.
6. The improved differential pulley constructed substantially as hereinbefore
described with reference to the accompanying drawings.
Dated this 29th day of January 1896.
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.