Improvements in or relating to Brakes for Hoists and similar Apparatus.
Year: 1897

page_text: Date of Application, 1st Dec., 1897-Accepted, 1st Dec., 1898
COMPLETE SPECIFICATION.
Improvements in or relating to Brakes for Hoists and similar
Apparatus.
I, ANTON BOLZANI, of 118, Invalidenstrasse, Berlin N, in the Empire of Germany,
Manufacturer, 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:-
All brakes for hoists and the like acting by means of a screw thread have the
drawback, that the pressure of the brake surfaces against each other is effected too
strongly by the screw, unless the pitch of the screw thread is so great that the
brake is automatically_driven_back_when_it_is_applied_in_which case, however, the
braking action becomes illusory or ineffective. The consequence is that with a
screw of fine pitch, to release the brake a comparatively great effort must be
applied whereby the brake is also released too much, so that the lowering of the
load takes place only by jerks or with the brake applied alternately too strongly
and too little that is to say, in a very unequal manner. The difference between the
friction of rest and the friction of motion also makes itself unfavourably noticeable
in this case thus making the working still more unequal.
This invention relates to a device for screw thread brakes by means of which
the lowering of the load is effected with the greatest possible and hitherto unattain-
able facility, without jerks or shocks, and besides the stoppage of the load when
desired is ensured even when the hoist is moving quickly.
The device according to the present invention is shown in Fig. 1 in axial section,
and in Fig. 2 in section on the line of Fig. 1, at right angles to the axis,
Figs. 3 and 4 showing respectively a horizontal axial section and an elevation of
the screw threaded disc.
C
On the squared portion a¹ or the like of the shaft a of the hoist is mounted a
disc or a fixed collar b. Against this disc or collar rests a flanged disc e provided
on its outer circumference with ratchet teeth e, said disc or ratchet wheel being
capable of rotating only in the direction of hoisting indicated in Fig. 2 by an
arrow; a pawl d pivotted on the frame engaging with its teeth and prevented
from rotation in the opposite direction. On a screw threaded portion of the shaft
is mounted a screw threaded disc e which when rotating in the direction of the
arrow presses against the disc c owing to the direction of the screw thread,
the latter disc o being thus clamped between said disc e and the fixed collar bon
the shaft.
To cause the discs to engage with each other or to become disengaged, the
following mechanism is employed;
C
The disc c has a cylindrical flange c² with inner circumferential teeth ³ with
which engages a toothed pinion g. The latter is mounted loosely on a stud f secured
to the screw threaded disc e and rolls on the inner toothed rim in whatever
direction rotation takes place. The hand chain wheel crank or the like driving
part h of the hoist is mounted loosely on an extension a³ of the shaft and is secured
to a spur wheel i which also engages with the pinion g. If the hand chain wheel

page_text: or the like is turned in one or in the other direction, the pinion y is caused to
rotate owing to its engagement with the spur wheel i, and the pin f moves in the
same direction as the pinion rolls on the toothed rim . The result will be that the
disc e will also participate in this movement, and, according to the direction of
movement, it will move on the screwthreaded portion of the shaft either towards
the brake disc o or away from it, so that the brake will be either applied or disen-
gaged. Of course a continuous rolling of the pinion g on the toothed rim only
takes place during the lowering of the load in lifting; it ceases as soon as the disc c
is clamped between the parts b and c, so that on the further rotation of e, c also
participates in this movement.
The arrangement of the described annular gearing for actuating the brake has
the important advantage that the force to be applied at the hand wheel for apply-
ing or disengaging the brake is very small, so that the risk of too great a pressure
or too sudden release is prevented. The annular gearing acts moreover as a regulat-
ing device, as owing to the rate of transmission required, the hand wheel must make
twice as many revolutions-under the assumption that the load exercises a driving
effort as the disce e whereby a considerable resistance is offered by the hand wheel,
said resistance being still increased by the hand-chain passing through the chain
guides when moving very quickly. The consequence is that even when the work-
man causes the hand-chain to move with a great speed, no injurious effects of the
momentum of the moving masses become noticeable, as the disc e always lags
behind the hand-wheel so that the load causes an automatic screwing and braking
action.
Another construction resulting in slightly different rates of transmission consists
in the part serving as a locking nut being secured to the spur-wheel i, while the
driving part of the machine carries the pin f with the pinion g. All the other
parts and their functions remain the same.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what I
claim is:
1. A brake for hoists and similar apparatus in which a brake disc adapted to
rotate, only in one direction is clamped between a fixed collar and a screw threaded
disc on the shaft, characterised by the screw threaded disc being operated by an
annular gearing mounted on the same spindle, substantially as described.
2. A brake for hoists and similar apparatus of the character described comprising
a screw threaded disc provided with a stud carrying a pinion loose on the latter,
said pinion engaging with the inner toothed rim of a brake disc and also with a
spur wheel secured to the driving part of the hoist loose on the shaft substantially
as described.
3. The combination and arrangement of parts constituting the complete brake
for hoists and similar apparatus substantially as described and illustrated in the
accompanying drawings.
1
1
1907