Improvements in Brake Mechanism for Lifts, Fire-escapes, and the like.
Year: 1889

page_text: Date of Application, 20th Nov., 1889-Accepted, 15th Nov., 1890
COMPLETE SPECIFICATION.
Improvements in Brake Mechanism for Lifts, Fire-escapes, and
the like.
A communication from PER GUNNAR BACKMAN, of 95, Boulevard Beaumarchais,
Paris, France, Inventor.
I, ALFRED JULIUS BOULT M.I.M.E. of 323 High Holborn, in the County of Middlesex,
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:-
The present invention relates to improvements in brakes for passenger or goods
lifts, fire-escapes and the like and its object is to prevent accidents in case of one of
the ropes or chains by which the cage of the lift is suspended, breaks.
In the accompanying drawings
Fig. 1 represents in vertical section the lift cage with its guides and safety
appliances.
Fig. 2 is a horizontal section of the lift on the line C-D of Fig. 1.
Fig. 3 is another horizontal section on the line E-F of Fig. 1.
Fig. 4 represents the brake in its ordinary position.
Fig. 5 is a sectional view of the brake when the cables are broken.
Fig. 6 is a sectional view of a modified form of brake and
Fig. 7 is a horizontal section of Figure 6.
A shows the cage suspended by two cables H Figure 1. B represents the tubes
which serve the cage as guides. C are two screw-threaded rods passing through the
tubes B. D are the movable nuts upon the rods C and are attached to the cage with
which they travel up and down.
E represent brackets connected with the cage, the inner surfaces of which
brackets correspond with the outer surfaces of the nuts D and are in this ordinary
position separated by a space the length or extent of which may be adjusted at
will.
I is a shaft placed above or beneath the cage and upon which are fixed two
cranks and two lever arms to the latter of which the ends of the cables are attached
one to each such arm.
G is a rod which is guided by the cage and can be raised or lowered by a turn of
the shaft I.
F represents a sleeve connected with the rod G, and attached to the nut D so that
it will travel up and down with the cage and prevent the said nut D from descending
at a greater speed than its own. The pitch of each of the screw-threaded columns is
such as to allow the nut D to travel upon it by the effect of its own weight or by the
pressure of the sleeve.
The nuts D travel with the cage up and down without causing any particular
friction as a permanent space exists between the parts E.
The brake itself is so constructed that if a breakage of the cable should occur
it would bring the parts D and E in contact so as to exert frictional resistance
sufficient to prevent the nut D from revolving whereby as a result the cage would
remain suspended upon the rods by means of the nuts. In addition to the above
described arrangement the contact surfaces of the nut D and the parts E so operate
in conjunction with each other that the produced friction will be sufficient to effect
the desired result but if necessary the engaging faces of D and E may be provided
with prongs or they may be smoothed or be of a conical or other desired shape.
The stoppage of the cage is therefore effected by the difference of speed between
the cage and the nuts D whereas such difference can only be produced by the
breaking of the cable or of those parts by which the cable connected with the cage.

page_text: In the accompanying drawing the cage is represented as suspended by two cables H
which are connected with the shaft I on the right and left of its axis. The shaft will
retain its position as long as the two cables are of the same length but as soon as one
of them should become longer or break, the shaft would lose its balance and would
turn round and raise the two rods G to which are attached the sleeves F connected
with the nuts and whereby the said nuts are moved into contact with the parts E.
The screw threaded columns can be made of any material and may consist of one
single piece or they may be made of several bars twisted together and a metallic cable
could be used in place of the rods. The nuts I have the same twist or pitch of thread
as the cable and either the screw-threaded columns or the cables may serve as guides
to the cage.
The tubes B are therefore not indispensable but they serve to guide the cage and to
enclose the cables and mechanism of the brake. It is quite clear that the principle of
the brake would remain the same even if the rod were omitted or the nut
connected to cords placed in the inner part of the two hollow tubes (see Figs. 6 and 7)
or with two toothed racks which would as it were simply form a longitudinal section
of the hollow tubes.
In Figures 6 and 7 the screw A placed within the slit tube B is supported by a
double bracket or frame C, a, b, the part of which is hollow so as to receive the
rod G connected to the horizontal shaft I by means of a link d and crank e.
Above the screw A and within the screw threaded upright B there is arranged a
piece E, the lower portion of which is hollow or recessed and fits exactly the shape of
the upper portion of the screw A. This piece E is connected to the cage by the
support or arin H and provided with an extension K in which slides the end of the
rod G. The arm. Hand extension_K_pass through the slot of the-screw-threaded.
column B.
Each of the cables L supporting the cage is connected to the shaft I. It passes
through a hole in the cage, then through the slot in the screw-threaded post and
finally enters the hollow piece E.
The screw thread on the hollow post is inclined at a very steep angle. Besides the
weight of the screw A is comparatively great. For these two reasons the screw A has
a constant tendency to descend.
-The consequence is that whether the lift rises or moves down the portion Cab
constantly rests upon the collar M fixed to the rod G. So long as the descent takes
place under normal conditions the top of the screw A can never come in contact with
the piece E.
Should one of the cables break however the shaft I as before stated being drawn in
one direction by the other cable begins to turn and causes the crank e and link d
to revolve with it. The rod G then in rising moves the bracket c through the
-medium of the sleeve M with the result that the screw A comes into contact with the
piece E.
The considerable amount of friction which then takes place effectively prevents the
screw A from turning and consequently arrests the descending cage.
It will be noticed that the lower portion of the piece E is slotted on one side so as
to receive.the arm a.
The nuts can be arranged to slide or to roll upon rollers and if desired the said nuts
may be stationary and the mountings and screws be the movable parts. In the
accompanying drawings the shaft I is placed beneath the cage but it could just as
well be placed above it or in any other suitable position.
Any suitable form of governor may be applied to the apparatus to control the speed
at which the cage travels.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to
me by my foreign correspondent I declare that what I claim is :-
1. In apparatus such as described the combination with a fixed screw or the
like of a nut carried by the moving part of the lift and so arranged that so long

page_text: as the hauling rope is in its normal condition the nut will revolve upon the screw
during the ascent or descent of the said moving part but when the rope breaks
the said nut will be jammed against an arm bracket or the like so that it will be
prevented from rotating and thus support the said moving part substantially as herein
described.
2. In apparatus such as described the combination with a revolvable screw or the
like of a nut carried by the moving part of the lift so that it is incapable of
rotating and so arranged that when the hauling rope is in its normal condition
the nut when moved up and down by the said moving part will cause the screw
to rotate but when the rope breaks the said nut will be jammed against a projection
or the like carried by the cage so as to prevent the screw from turning substantially
as herein described.
3. In apparatus such as described a stationary screw cable or long divided nut such
as C a screw or nut such as D engaging therewith, sleeve E a sleeve or supporting
arm such as F and rod G-so connected to the cage and by means of shaft and lever
arms to the hauling rope that when the rope breaks the nut or screw will become
jammed and will prevent the cage from falling substantially as described and illus-
trated in the accompanying drawings.
Dated this 20th day of November 1889.
W: P. THOMPSON & BOULT,
Agents for the Applicant.