Improvements in and relating to Strap Brakes, specially suitable for Capstans, Steam Winches, and the like, and applicable also to Friction Clutches.
Year: 1894

page_text: Date of Application, 30th Mar., 1894
Complete Specification Left, 29th Dec., 1894-Accepted, 2nd Feb.. 1895
PROVISIONAL SPECIFICATION.
Improvements in and relating to Strap Brakes, specially suitable for
Capstans, Steam Winches, and the like, and applicable also to
Friction Clutches.
1, THOMAS MAXWELL GRANT, and ALEXANDER KELLY, both of the Firm of
Napier Brothers, Limited, Engineers, 100 Hydepark Street, in the City and
County of Glasgow, and CHRISTIAN DETHLEFF BIRCK HANSEN, Draughtsman
to said firm, do hereby declare the nature of our invention to be as follows:-
This invention has reference to and comprises an improved differential self
holding strap brake for machinery in general, but specially suitable for capstans or
cable wheels, steam winches, and the like, and which will operate whether the
capstan or machine is rotated in the one direction or the other; the improvements
being also applicable to friction clutches.
As applied to a cable capstan with the usual vertical spindle and rotating cover
with cable wheel, the improvements consist in fitting over the basement fixed flange
of capstan two short vertical stud spindles or uprights, one on each side of the
usual central vertical spindle. A semicircular or segmental horizontal frame is
fitted within the outer cover, and is formed with segmental socket recesses to
embrace the two stud spindles. A horizontal flange plate would project out from
the centre of this frame through the cover and be formed with a segmental toothed
rack on its outer face, so as to be operated by wheel or lever gear to shift the
inner frame to be in contact with the one stud spindle or the other to apply the
brake, according to the direction the capstan is for the time being turning. A
brake strap is applied intermediate between the segmental eccentric acting frame
and the inner surface of the outer rotating cover. This brake strap would or may
consist of a spring ring, split or duplex for say three-fourths of its circumference
to have top and bottom webs or segmental rings coming round annularly from one
end, and a central web or segmental ring coming round from the other end in the
intermediate open space for half the circumference between the top and bottom
segmental rings of the previous end, the ends of these rings being free, all so as to
form a brake strap with one and a half turns as it were. The inner segmental
frame is formed with projecting surfaces or flanges at its extreme outer ends to bear
on the split rings of brake strap, the one bearing surface being preferably formed
with a small recess to receive and guide the central segmental ring, while the free
ends of the duplex rings bear on the face of one flange and the free end of the
single ring on the face of the opposite flange.
In applying the brake, the inner segmental frame would be operated through
its central projecting flange plate and the actuating hand gear to turn on the
eccentric spindle desired, according to the direction the capstan is for the time
being revolving, and the brake strap will with a differential action act on the
rotating outer cover to stop or retard its motion. By this means the one end of
the strap which bears on the projecting flange of the shorter arm of the inuer
segmental frame is relieved to some extent, while the other end of the strap which
bears on the projecting flange of the longer arm of the frame is tightened, and the
total tightening effect is thus equal to the difference of these two actions.
In capstans or machines where the strap brake is only desired to be applied in
one direction of rotation, the inner segmental frame would only require to be formed

page_text: with one segmental socket recess to bear on one upright spindle to give differential
action.
In applying our improvements to friction clutches instead of using a projecting
toothed plate we form projecting lugs with bevelled or angled faces on the one
surface of the segmental frame, and mount a loose collar on the shaft to be coupled,
so that when the clutch is to be put in gear .this collar is made to slide along the
shaft and force the segmental frame outwards towards the circumference of the
revolving drum or pulley, and thus press the spring strap against said circunference,
when the friction will take the strap and segmental frame round until the latter
bears on one or the other of the stud spindles, and thus bring the differential action
of the segmental frame into play. In like manner the shifting of the loose collar
on shaft will bring the segmental frame in towards the centre, and relieve the strap
from contact with inner circumference of pulley.
Dated the 29th day of March 1801
W. R. M. THOMSON & Co.,
96, Buchanan Street, Glasgow, Agents.
COMIDELE DF ECIFICATION.
Improvements in and relating to Strap Brakes, specially suitable for
Capstans, Steam Winches, and the like, and applicable. also to
Friction Clutches.
We,
THOMAS MAXWELL GRANT, and ALEXANDER KELLY, both of the Firm of
Napier Brothers, Limited, Engineers, 100 Hydepark Street, in the City and
County of Glasgow, and CHRISTIAN DETHLEFF BIRCK HANSEN, Draughtsman
to said firm, do hereby declare the nature of our invention, and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement in writing, that is to say :-
This invention has reference to and comprises an improved differential self
holding strap brake for machinery in general, but specially suitable for capstans or
cable wheels, steam winches, and the like, and which will operate whether the
capstan or machine is rotated in the one direction or the other; the improvements
being also applicable to friction clutches.
And in order that our said invention and the manner of performing or carrying
the same into effect or practice may be properly understood, we have hereunto
appended an explanatory sheet of drawings in which the same reference letters are
used to indicate corresponding parts in all the figures where shown.
Figure 1 is a sectional elevation of a capstan as fitted with our improvements.
Figure 2 is a plan view corresponding to Figure 1 with the outer cover
removed, and
Figure 3 is an outside elevation corresponding to and at right angles to
Figure 1.
Figure 4 is a perspective view showing our spring strap brake.
Figure 5 is a sectional elevation showing our improvements applied as a friction
clutch to shafting, and
Figure 6 is an external view corresponding to and at right angles to Figure 5.
Referring to these drawings:-As applied to a cable capstan with the usual
vertical spindle A and rotating cover A¹ with cable wheel, as shown in Figures 1
to 3, the improvements consist in fitting over the basement fixed flange Z of capstan
two short vertical stud spindles or uprights bb one on each side of the usual
central vertical spindle A. A semicircular or segmental horizontal frame B is fitted
within the lower part A' of the outer cover A., and is formed with segmental
socket recesses at 6' to embrace the two stud spindles b. A horizontal flange
plate B would project out from the centre of this frame B through or under the

page_text: cover A' and be formed with a segmental toothed rack B' on its outer face, so as to
be operated by wheel or lever gear preferably a lever a with lower toothed
segmental pinion a¹ fulcrumed at a² so as to shift the inner frame B to be in contact
with the one stud spindle or the other to apply the brake, according to the
direction the capstan is for the time being turning. A brake strap C is applied
intermediate between the segmental eccentric acting frame B and the inner surface
of the outer rotating cover A' A. This brake strap would or may consist of a
spring ring C split or duplex for say three-fourths of its circumference to have top
and bottom webs or segmental rings C³ C2 coming round annularly from one end
and terminating at c and a central web or segmental ring C coming round from the
other end in the intermediate open space for half the circumference between the
top and bottom segmental rings C₁C? of the previous end, and terminating at c¹
the ends cc of these rings C1 C2 C, being free, all so as to form a brake strap
with one and a half turns as it were the rings being preferably jointed at C³ as
shown in Figure 2. The inner segmental frame B is formed with projecting
surfaces or flanges at its extreme outer ends to bear on the split rings C C1 C2 of
brake strap, the one bearing surface being preferably formed with a small recess
at 2 to receive and guide the central segmental ring C, while the free ends of the
duplex rings C1 C2 bear on the face of one flange at this part 2 and the free end
of the single ring C on the face of an opposite projecting flange or rib at 6³.
In applying the brake, the inner segmental frame B would be operated through
its central projecting flange plate B' and the actuating hand gear a to turn on the
eccentric spindle 6 desired, according to the direction the capstan is for the time
being revolving, and the brake strap will with a differential action act on the
rotating outer cover A1, A2, to stop or retard its motion. By this means the one
end of the strap C or C1 C2 which bears on the projecting flange of the shorter
arm of the inner segmental frame B is relieved to some extent, while the other end
of the strap which bears on the projecting flange of the longer arm of the frame B
is, tightened, and the total tightening effect is thus equal to the difference of these
two actions.
In capstans or machines where the strap brake is only desired to be applied in
one direction of rotation, the inner segmental frame B would only require to be
formed with one segmental socket recess 6¹ to bear on one upright spindle b to give
differential action.
In applying our improvements to friction clutches, as shown in Figures 5 and 6,
instead of using a projecting toothed plate we form projecting lugs B³ with beveled
or angled faces B2 on the one surface of the segmental frame B and mount a loose
collar or sleeve D on the shaft to be coupled, so that when the clutch is to be put
in gear this collar D is made to slide along the shaft and force the segmental
frame B outwards towards the circumference of the revolving drum or pulley A*
and thus press the spring strap C C1 C2 against said circumference, when the
friction will take the strap and segmental frame B round until the latter bears on
one or the other of the stud spindles b and thus bring the differential action of the
segmental frame B into play. In like manner the shifting of the loose collar D on
shaft will bring the segmental frame Bin towards the centre, and relieve the brake
strap from contact with inner circumference of pulley A³.
The revolving drum or cover A² is keyed at e to the part E of shaft, and an
enclosing disc D¹ is keyed at e¹ to the other coupling part E of shaft, the spindles b
being formed on said disc, recesses being formed in the disc for the projecting
toothed lugs B¹ B² to pass through.
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:—
First. The arrangement and use of a differential self holding strap brake,
constructed to act substantially as herein described, in reference to and by way of
application shown in the accompanying drawings.

page_text: Second. In capstans, steam winches, and the like, the arrangement and use of an
eccentric acting frame, with spring interposed between said frame and an outer
cover so as to form a differential self holding strap brake substantially as herein
described in reference to and shown in Figures 1 to 4 of the accompanying
drawings.
'
Third. In friction clutches for shafting and the like the arrangement and use of
an eccentric acting frame, with spring interposed between said frame and an outer
cover, and acting substantially as herein described in reference to and shown in
Figures 5 and 6 of the accompanying drawings.
Dated the 28th December 1894.
W. R. M. THOMSON & Co.,
96, Buchanan Street, Glasgow, Agents.