Improvements in Extension-ladders.
Year: 1892

page_text: Date of Application, 28th Apr., 1892
Complete Specification Left, 28th Jan., 1893-Accepted, 8th Apr., 1893
PROVISIONAL SPECIFICATION.
Improvements in Extension-ladders.
I, GEORGE BRAY, of 440 New Cross Road, in the County of Kent, Engineer,
do hereby declare the nature of this invention to be as follows:-
My invention relates to improvements in extension-ladders.
The object of my said invention is to provide improved means whereby the
upper length of extension-ladders, fire-escapes and the like, which slides upon the
lowermost or main length of the ladder, is prevented, when the elevating rope,
wire or the like ceases to support the said lengths by reason of its breakage or
owing to other causes from suddenly falling back to its original position after
having been elevated. Serious accidents have heretofore resulted from the sudden
collapse, in such a manner, of extension-ladders when in use at fires and on other
occasions.
According to my said invention I provide one or more hooks, pawls or the like
upon the sliding portion of the ladder, to which hooks pawls or the like the hoisting
or elevating wire or rope is secured so that as long as the tension of the said rope
is exerted through the medium of the said hooks, or pawls for example to support
the ladder the hooks or pawls are maintained out of engagement with the rungs
of the ladder or other suitable projections on the ladder with which they are
adapted to engage. For example a pair of hooks may be hinged to the movable
length of the ladder, and provided with short arms of extensions to which the
hoisting line is secured. The said hooks may be so shaped as to be suited to
engage with the rungs of the main ladder, and may be weighted or provided with
suitable springs so that immediately on the cessation of the pull of the line the
hooks would be forced into position to engage with the said rungs.
The said springs or weights are arranged so that they may be readily adjusted
in order that they may not act to throw the hooks or pawls into operation when
the tension thereon is lessened in the operation of lowering the ladder.
Obviously the lifting line or lines need not be directly secured to the hooks or
pawls, but may act upon suitable mechanism which will keep the said pawls or
hooks out of action so long as the hoisting line is kept in tension.
The same apparatus may be applied with equal advantage to ladders which
have more than one sliding or extra length, in which case pawls or hooks arranged
as aforesaid are applied to each length, and engage, when released, with the
adjacent length of ladder.
Instead of providing projections for the said pawls or hooks to engage with, I
may use friction-pawls, wedges clutches or other means so arranged that they are
kept out of action by the lifting line and put into readiness for automatic action
by any breakage or slackening of the said line.
Dated this 28th day of April 1892.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Extension-ladders.
I, GEORGE BRAY, of 440 New Cross Road, in the County of Kent, Engineer,
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:-
My invention relates to improvements in extension-ladders.

page_text: The object of my said invention is to provide safety devices, whereby the upper
length of extension ladders, fire-escapes and the like, which slides upon the lower-
most or main length of the ladder, is prevented from suddenly falling back to its
original position after having been elevated, in the event of breakage or accidental
slackening or release of 'the elevating rope, wire or elevating gear. Serious
accidents have heretofore resulted from the sudden collapse, in such a manner, of
extension-ladders when in use at fires-and on other occasions.
In order that my said invention may be clearly understood I will now proceed
to describe the same with reference to the accompanying drawings, wherein
Figure 1 represents in front elevation, portions of an extension-ladder fitted
with improvements according to my invention,
Figure 2 is a vertical section on the line xx of Figure 1,
Figure 3 is a view, similar to Figure 2, of apparatus constructed according to
my invention alternative to that illustrated in Figures 1 and 2, and
Figures 4, 5 and 6 are views similar to Figure 1, showing further alternative
devices.
Like letters of reference indicate corresponding parts throughout the drawings.
With reference first to Figures 1 and 2, A is the main ladder, B is an extra
ladder which slides thereon. "A¹ A¹ are the rungs of the ladder A, and B¹ B' are
the rungs of the ladder B. CC are cranked levers, pivoted at B2 to the verticals
of the ladder B as shown. Each lever C has one of its arms C" formed as a claw
or hook adapted to engage with the rungs A¹ of the ladder A; the other arm C³ of
each lever C is adapted for the attachment thereto of a connection D to the
elevating-rope E. FF are springs, one of which is secured by one end to each of
the arms C G G are brackets or lugs on the ladder B, to which the opposite
ends of the said springs Fare adjustably connected. H H are stops secured to the
ladder B, to limit the movement of the levers C about their pivots B³.
rungs
A'
As long as the tension of the elevating-rope E is exerted through the medium of
the levers C to support the ladder B, the hooks or claws C¹ are maintained in the
position in which they are shown in dotted lines, out of engagement with the
or other suitable projections on the ladder A; but immediately upon a sufficient
diminution of the pull of the rope E the springs F act to force the levers C into
such a position that immediately upon the descent of the ladder B the claws or
hooks C on the said levers will engage with the rungs A¹ as shown in full lines
in the drawing.
The springs F are so adjusted that they will not act to move the hooks or
claws C towards the ladder A until the tension on the rope is lessened to a
greater extent than the lessening necessary in the operation of lowering the
Ladder B.
Instead of springs the arms C³ of the levers C may be extended, and adjustable
balance-weights placed thereon in substitution for the springs F.
In the apparatus illustrated in Figure 3, struts I are substituted for the hooks or
claws C' of the levers C. The said struts are caused to bear upon the upper sides
of the rungs A¹ of the ladder A when the tension on the rope E is sufficiently
lessened. The struts are brought into or out of operation in a manner similar to
the operation of the levers C, Figures 1 and 2.
In the apparatus illustrated in Figure 4 a lever J is pivoted at B' at each side of
the ladder B. The short arm J' of each said lever is formed as a friction cam of
increasing radius relatively to B and is arranged to bear upon the inner face of the
verticals of the ladder A. The long arm J of each lever J is connected to the
elevating-rope or wire E. H H are stops to limit the upward movement of
the arms J**
As long as sufficient tension is maintained upon the arms J³ they are kept against
the stops H and the ladder B can be raised by the action of the rope E thereon,
through the medium of the said arms and stops. But if the tension upon the rope E
be lessened by breakage of the same or otherwise, the friction between the end of
each arm J' and the contiguous portion of the ladder A will rotate the said arms,

page_text: as the ladder B commences to descend, until the portions of the cams on the arms J'
move outward from the sides of the ladder B and by the resulting increase of
friction between the said cams and the ladder A, stop the downward movement
of the said ladder B. The ends of the arms J' and the portions of the ladder
on which they bear, can be roughened if desired to increase the friction between
them.
In the arrangement illustrated in Figure 5 the inner faces of the verticals of the
ladder A are provided with ratchet teeth A' and bolts K are arranged to slide
transversely in guides K' secured near the bottom of the ladder B. F is a spring
which is placed between the inner ends of the bolts K and tends to force both of
them outward towards the ladder A.
LL are levers the arms L¹ of which are pivoted to the bolts K at K* and pivoted
to each other at L³, where they cross. The arms L of the levers L are connected
by lines D to the elevating rope E. H H are stops to limit the inward movement.
of the bolts K. As long as sufficient tension is exerted upon the said elevating rope
the arms are drawn together and the bolts K kept at the inward extreme of
their travel. With the parts in this position the ladder B may be raised by the pull
on the rope E which is transmitted thereto through the said levers and bolts.
When the tension on the rope E is sufficiently lessened the spring F forces the
bolts K outward into engagement with the ratchet teeth A, to prevent the descent
of the said ladder B. As an alternative, the levers L can be pivoted to a cross-bar
of the ladder B, as well as to each other, and connected to the bolts K by pin-and-
slot connections.
In the apparatus illustrated in Figure 6 the ladder A. is provided with ratchet
teeth A, and the bolts K arranged to slide in guides K' on the ladder B, are each
provided with a separate spring F and are connected by flexible connections D' to
the elevating rope E. The said connections are passed over sheaves M placed in
suitable bearings at the lower end of the ladder B, so that a sufficient diminution of
tension in the rope E and connections D¹ allows the springs F to push the bolts out
into engagement with the ratchet teeth A². Conversely, a sufficient increase of
tension in the rope E and connections D' causes the latter to pull the bolts in along
their guides, and effects the raising of the ladder B.
Obviously the lifting line or lines need not be directly secured to the locking
devices, but may act upon suitable mechanism which will keep the said devices out
of action so long as the hoisting line is kept in tension.
The same apparatus may be applied with equal advantage to ladders which have
more than one sliding or extra length, in which cases pawls hooks or other devices
arranged as aforesaid are applied to each length, and engage, when released, with
the adjacent length of ladder.
Instead of the devices herein before described I may use for like purposes, any
suitable form of clutch or other appliance so arranged as to be kept out of action by
the elevating-wire, rope, or gear, and put into readiness for automatic action by the
breakage or by the accidental slackening or release of the same.
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 :-
1. An automatic safety-device applied to extension-ladders in such a manner as
to become operative upon the breakage or accidental slackening of the elevating
wire, rope or gear, for the purpose specified.
2. The automatic safety devices for extension-ladders, substantially as herein-
before described with reference to Figures 1 and 2 or to Figure 3, Figure 4,
Figure 5, or Figure 6 of the accompanying drawings, for the purposes specified.
Dated this 28th day of January 1893.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.