IMPROVEMENTS IN AUTOMATIC SAFETY APPLIANCE FOR ELEVATORS
Year: 1884

page_text: I JOHN HENRY JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman, do hereby declare the nature of said Invention for "IMPROVEMENTS
IN AUTOMATIC SAFETY APPLIANCE FOR ELEVATORS," and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement :-
This Invention is an improvement upon an Invention described in the
Specification of Letters Patent Number 287 287 granted for the United States to
my foreign correspondent and dated October Twenty-third One thousand eight
hundred and eighty three as the same is improved by the Invention covered by an
application for a Patent for the United States filed by my foreign correspondent in
the United States Patent Office on October First One thousand eight hundred and
eighty three.
In the apparatus forming the subject matter of the said Patent and application
the elevator in case of accident was immediately arrested on its fall upon the
withdrawal by the person operating the same of his foot from the treadle inside of
the car according to the present Invention the treadle is dispensed with and there
is substituted therefor mechanism which causes the car to be arrested automatically
in case it should fall by the breaking of the ropes or by other accident.
The Figures of the accompanying Drawings represent the improvements
constituting the present Invention.
Figure 1 is a front view of an elevator car and its upright side supports with
the present improvements attached as the same appears when the elevator car is
descending.
Figure 2 is a front view of an elevator car and its upright side supports with
the said improvements attached as the same appears when the elevator car has
dropped as in case of accident so as to engage the dogs or projections.
In the usual upright supports or posts between which the elevator car slides a
series of dogs or projections are provided they being so pivoted or hinged that they
will at once be sprung out or fall out by their own gravity into their normal
position to engage the bottom of the elevator car should it descend against them
immediately below and on each side of the parts of the floor of the elevator car

page_text: which would otherwise rest upon the dogs or projecting hinged pieces when they
have assumed their normal position a bar or piece is provided the object of which
is to cause the dogs or projections to be raised up out of the way of the floor or
bottom of the elevator car so as to enable the said car to descend.
These bars or side pieces are so bevelled that when they are raised up against
the bottom of the car the edges of the dogs or hinged projections in the supports or
posts are engaged by them as the elevator descends and the said dogs or projections
are pushed back out of the way of the said car so as to enable it to proceed in its
descent. In passing upward the elevator car itself pushes the dogs or projections
out of the way but in descending the said dogs or projections are only pushed out
of the way when the bevelled bars or side pieces on the car are in position. A
weight acting by means of a pulley and rope or chain serves to raise the bevelled
bars or side pieces into position so as to cause them to engage the dogs or
projections on the supports or posts and push them out of the way of the descending
car. A spring on each side operates in opposition to this weight, the tendency of
the springs being to cause the bevelled bars or side pieces to be withdrawn
instantly so as not to engage the dogs or projections in the supports or posts.
In case any accident should cause the fall of the car, the relation of this weight
to the spring is instantly so disturbed that the springs are enabled to act to
withdraw the bevelled bars or side pieces thus causing the car to be immediately
arrested in its descent by the dogs or projections on the supports or posts.
In the Drawings a represents the floor of the elevator car, bb the vertical
supports or posts between which it slides, c c are the hinged dogs or projecting
pieces, d d are the bevelled pieces that serve to press back the dogs c into such a
position that they will allow the clevator car to descend without being arrested,
ee aro arms attached at right angles to the bevelled pieces d d, f is a piece upon
which the parts e e rest, g is a rope or chain upon which the piece f hangs, h is a
pulley over which the said rope or chain passes, i is a weight attached to the said
rope or chain, k k are the supports in which the piece d slides, l'Z are springs each
fastened to a support k and also to the bar or piece d in such manner as to tend to
withdraw the bars or pieces d out of the way of the dogs c.
"
The operation of this mechanism is as follows. When the weight is exerting
its normal pressure against the action of the springs the bevelled pieces d are
forced upward and outward into such a position as to engage or lie in the path of
the dogs or projections c, but should the supports of the elevator car give way, the
relation between the force exerted by the weight i and the force exerted by the
tension of the springs is instantly disturbed so as to cause the springs / to at once
act to withdraw the bevelled pieces d from the said position when the dogs o
instantly engage the bottom of the car which rests upon them so that its descent
is thereby arrested. The weight of the part f and of the parts resting upon it acts
in conjunction with the springs and in opposition to the weight i.
'In carrying out this Invention the use of the spring 7 is not absolutely necessary.
The weight of the part fand of the parts resting upon it may be so proportioned
to the weight of i that the apparatus will arrest the car in case of accident
without requiring springs but springs are preferred on account of the certainty
and quickness of their action.
It will be evident from the foregoing description that the moment the elevator
car falls in case of accident the tension upon the rope g supporting the weight i
is instantaneously lessened thus enabling the springs to operate and as the
slightest withdrawal of the bevelled parts d prevents the dogs c from being
forced out of the way of the clevator car, the car is instantly arrested by the said
dogs and this with absolute certainty.
It is obvious that the weight i must be heavy enough to overcome the gravity
of the part fand the parts resting upon it, and also the tension of the springs.
It is also obvious that if the part finstead of being suspended by a rope, as
shewn was suspended to the bottom of the car by means of a spring of suitable

page_text: tension, such a contrivance would be the mechanical equivalent of that which I
have described but I prefer the weight.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is
First-In safety apparatus for elevators. Projections adapted to arrest an
elevator car in combination with mechanism to engage the projections and throw
them out of the way of the elevator car as it descends and a spring or springs
operating to withdraw said mechanism which engages the projections so as to
allow the projections to stop the descending car and mechanism adapted to hold
the mechanism engaging the projections in the position which engages the
projections except in case of accident substantially as herein before described.
Second-In safety apparatus for elevators the combination of the projections c
bevelled pieces & springs and the weight or its equivalent arranged and operating
substantially as hereinbefore described with reference to the accompanying
Drawings.
-
Third-In safety apparatus for elevators the combination of the projections o
the pieces d, e, the piece f the springs 1, the rope or chain g (with a suitable pulley
or support) and the weight i arranged and operating substantially as herein before
described with reference to the accompanying Drawings.
"