Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
[0001] HYDRAULIC ELEVATOR SAFETY APPARATUS
FIELD
[0002] There is described a safety apparatus intended to prevent a free
fall of an elevator
car of a hydraulic elevator in the event of a loss of hydraulic pressure due
to a single bottom
cylinder failure.
BACKGROUND
[0003] A hydraulic elevator has an underlying hydraulic cylinder which
serves to raise
and lower the elevator car. It was once assumed that a leak of hydraulic fluid
would merely
result in the elevator car slowly descending. There have now been some
catastrophic failures
due to hydraulic cylinder failures as a result of rust and hydraulic line
ruptures. These have
resulted in serious injuries and, in some instances, loss of life. One
solution which has been
proposed is to provide a sensor in combination with an overspeed valve which
will slow the
descent of an elevator car if an unacceptable rate of descent is sensed, as is
illustrated and
described in U.S. Patent 6,059,071 (Gilliland et al). The overspeed valve only
provides
protection against some types of failures, it not protect against hydraulic
cylinder failure.
Another solution which has been proposed are various devices which prevent
telescoping
movement of the hydraulic cylinder, as is illustrated and described in U.S.
Patents 3,995,534
(Rastetter); 6,039,151 (Ringel et al); 6,179,094 (Seggebruch et al); 6,206,145
(Cable et al);
and 6,478,123 (Seggebruch et al). One such device which prevents telescoping
movement of
the telescoping cyclinder is currently being marketed by Adams Elevator under
the
Trademark "Life Jacket". There will now be described an alternative solution.
SUMMARY
[0004] There is provided a hydraulic elevator safety apparatus for an
elevator having a
hydraulic cylinder which moves an elevator car up and down a vertical shaft.
The apparatus
includes a stop assembly that moves with the elevator car and consists of a
stop lever, at least
one elevator stop carried by the stop lever and a stop lever support which is
secured to the
frame of the elevator car. The stop lever is pivotally secured to the stop
lever support to
define a fulcrum. The lever pivots about the fulcrum between an inoperative
position and an
operative position. In the inoperative position, the elevator stop is
disengaged allowing the
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elevator car to move downwardly unimpeded. In the operative position, the
elevator stop
engages to prevent downward movement of the elevator car. A stop lever biasing
spring
biases the stop lever into the operative position. A stop lever hold-down
assembly is
provided that does not move with the elevator car and includes a hold-down
support and a
hold-down lever pivotally secured to the hold-down support and movable between
a stop
lever retention position and a stop lever release position. A cable guide is
mounted to the
hold-down lever. A follower cable is provided having a first end secured to
the stop lever
and a second end secured to the elevator car. The cable extends around the
cable guide of
the hold-down lever, such that the cable moves around and is guided by the
cable guide as
the car goes up and down. As long as the hold-down lever is maintained in the
stop lever
retention position, the cable exerts a force upon the stop lever to overcome
the force of the
stop lever biasing spring and maintain the stop lever in the inoperative
position. A pressure
monitoring hydraulic actuator is provided which includes a hydraulic cylinder
and a piston
movable in the hydraulic cylinder. The piston has a piston rod connected to
the hold-down
lever. Movement of the piston in a first direction moves the hold-down lever
to the stop
lever retention position. Movement of the piston in a second direction,
opposed to the first
direction, moves the hold-down lever to the stop lever release position
slackens the cable. A
hydraulic connection is maintained between the hydraulic lifting cylinder for
the elevator car
and the hydraulic actuator. As long as hydraulic pressure is maintained at
operating levels,
the piston of the hydraulic actuator is urged in the first direction to
maintain the hold-down
lever in the stop lever retention position. Upon a loss of hydraulic pressure,
the piston of the
hydraulic actuator moves in the second direction to the stop lever release
position and
slackens the cable, whereby the biasing force of the stop lever biasing spring
moves the stop
lever into the operative position with the elevator stop engaging to prevent
downward
movement of the elevator car.
[0005] As will hereinafter be described, in most installations an
elevator car travels
along guide rails. It is, therefore, preferred that the stop lever support is
mounted to the
frame of the elevator car in proximity to one of the guide rails. When the
stop lever is in the
inoperative position the elevator stop is positioned in parallel spaced
relation to the one of
the guide rails and moves along the guide rails with the elevator car. When
the stop lever is
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in the operative position the elevator stop frictionally engages the one of
the guide rails to
develop a rapidly increasing pressure on the guide rails during a stopping
interval and
thereafter prevent further downward movement of the elevator car.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] These and other features will become more apparent from the
following
description in which reference is made to the appended drawings, the drawings
are for the
purpose of illustration only and are not intended to be in any way limiting,
wherein:
[0007] FIG. 1 is a side elevation view of a hydraulic elevator safety
apparatus.
[0008] FIG. 2 is a schematic hydraulic diagram for the hydraulic elevator
safety
apparatus illustrated in FIG. 1.
DETAILED DESCRIPTION
[0009] A hydraulic elevator safety apparatus generally identified by
reference numeral
10, will now be described with reference to FIG. 1 and FIG. 2.
Structure and Relationship of Parts:
[0010] Referring to FIG. 1, safety apparatus 10 is illustrated as it
would appear installed
in a pit 102 of a vertical shaft 104 of a hydraulic elevator 100. There is
illustrated elevator
car guide rails 106 and frame 108 of the elevator car. Although not
illustrated, it will be
understood that the elevator car is positioned on frame 108 and that there is
a single
hydraulic lifting cylinder also positioned in pit 102 moves frame 108 up and
down vertical
shaft 104.
[0011] A stop assembly, generally identified by reference number 12, moves
with the
elevator car. Stop assembly 12 includes a stop lever 14. An elevator stop 16
is carried by
stop lever 14. A stop lever support 18 is secured to frame 108 of the elevator
car. As is
illustrated, stop lever 14 is pivotally secured to stop lever support 18 to
define a fulcrum 20.
Stop lever 14 pivots about fulcrum 20 between an inoperative position and an
operative
position. In the inoperative position, elevator stop 16 is disengaged allowing
the elevator car
to move downwardly unimpeded. In the operative position, elevator stop 16
engages to
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prevent downward movement of the elevator car. A stop lever biasing spring 22
biases stop
lever 14 into the operative position.
[0012] In FIG. 1, elevator stop 16 is illustrated as a pair of
cooperating wedges 16a and
16b. It will be appreciated that the configuration of elevator stop 16 may
vary. Stop lever
support 18 is mounted to frame 108 of the elevator car in proximity to one of
guide rails 106.
When stop lever 14 is in the inoperative position, wedges 16a and 16b of
elevator stop 16
are positioned in parallel spaced relation to guide rail 106. When stop lever
14 is in the
operative position, wedges 16a and 16b frictionally engages guide rail 106 to
develop a
rapidly increasing pressure on guide rail 106 during a stopping interval and
thereafter prevent
further downward movement of the elevator car.
[0013] A stop lever hold-down assembly, generally identified by
reference numeral 24,
is positioned in pit 102 and does not move with the elevator car. Hold-down
assembly
includes a hold-down support 26 and a hold-down lever 28 pivotally secured to
hold-down
support 26 and movable between a stop lever retention position and a stop
lever release
position. A cable guide 30 is mounted to hold-down lever 28. Cable guide 30 is
in the form
of a sheave and includes cable retainers 32.
[0014] A follower cable 110 is provided having a first end 112 secured to
stop lever 14
and a second end 114 secured to frame 108 of the elevator car. Cable 110
extends around
cable guide 30 of hold-down lever 28. Cable moves around and is guided by
cable guide 30
as the elevator car goes up and down. As long as hold-down lever 28 is
maintained in the
stop lever retention position, cable 110 exerts a force upon stop lever 14 to
overcome the
force of stop lever biasing spring 22 and maintain stop lever 14 in the
inoperative position.
[0015] A pressure monitoring hydraulic actuator is provided, generally
identified by
reference 34. Hydraulic actuator includes a hydraulic cylinder 36, and a
piston 38 movable
in hydraulic cylinder 36. Piston 38 has a piston rod 40 which is connected to
hold-down lever
28. Movement of piston 38 in a first direction, indicated by arrow 42, moves
the hold-down
lever 28 to the stop lever retention position. Movement of piston 38 in a
second direction
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opposed to the first direction, as indicated by arrow 44, moves hold-down
lever 28 to the
stop lever release position and slackens cable 110. It is preferred that a
piston biasing spring
46 be provided to bias piston 38 in the second direction.
5 [0016]
There is a hydraulic connection, in the form of a feed line 48 indicated by
arrow
48, between the hydraulic lifting cylinder (not shown in FIG. 1) for the
elevator car and
hydraulic actuator 34. Referring to FIG. 2, there is illustrated a preferred
hydraulic circuit.
Single hydraulic lifting cylinder is identified by reference numeral 120.
Hydraulic lifting
cylinder 120 receives hydraulic fluids for its normal operation through feed
line 122 which is
connected to a hydraulic pumping unit (not shown). A pair of pressure
monitoring hydraulic
acutators 34 are illustrated. The reason two are illustrated is that it is
preferred to have a pair
of elevator stops each acting upon opposed guide rails. Hydraulic actuators 34
are connected
to hydraulic lifting cylinder 120 by feed lines 48, so that they share
pressure with hydraulic
lifting system 112. It is viewed as desirable to include a manual shut off
valve 50 on each of
feed lines 48, to isolate hydraulic acutators 34 for purposes of servicing and
testing. In order
to make provision for testing, there should also be a testing connection line
52 with a testing
valve 54. Shut off valve 50, testing connection line 52 and testing valve 54
allows for
connection of equipment to vary the pressure in feed line 48 and test
operation of safety
apparatus 10 without involvement of hydraulic lifting cylinder 120.
Operation:
[0017]
Referring to FIG. 1, as long as hydraulic pressure is maintained at normal
operating levels, piston 38 is urged by hydraulic pressure in the first
direction to maintain
hold-down lever 28 in the stop lever retention position. As long as hold-down
lever 28 is
maintained in the stop lever retention position, cable 110 exerts a force upon
stop lever 14 to
overcome the force of stop lever biasing spring 22 and maintain stop lever 14
in the
inoperative position. When stop lever 14 is in the inoperative position,
wedges 16a and 16b
of elevator stop 16 are positioned in parallel spaced relation to guide rail
106.
[0018] Upon a loss of hydraulic pressure, piston 38 moves in the second
direction to the
stop lever release position, slackening cable 110. The movement of piston 38
in the second
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direction is accelerated by piston biasing spring 46 which biase piston 38 in
the second
direction. The slackening of cable 110 results in the biasing force of stop
lever biasing
spring 22 moving stop lever 14 into the operative position. When stop lever 14
is in the
operative position, wedges 16a and 16b frictionally engages guide rail 106 to
develop a
rapidly increasing pressure on guide rail 106 during a stopping interval and
thereafter prevent
further downward movement of the elevator car.
Variations:
[0019]
There are a variety of ways in which the elevator stops may be configured. The
preferred manner is a guide rail engagement with the operating force derived
entirely from
pressure applied on the guide rails through eccentrics, rollers, wedges, or
similar devices. It
is preferrable to avoid introducing any medium that might limit the braking
force.
Cautionary Warnings:
[0020] If the elevator stop is to engage the guide rails, the guide rails
must be installed in
the elevator pit in a manner that can withstand the forces experienced during
stopping.
[0021]
In this patent document, the word "comprising" is used in its non-limiting
sense
to mean that items following the word are included, but items not specifically
mentioned are
not excluded. A reference to an element by the indefinite article "a" does not
exclude the
possibility that more than one of the element is present, unless the context
clearly requires
that there be one and only one of the elements.
[0022] The scope of the claims should not be limited by the illustrated
embodiments set
forth as examples, but should be given the broadest interpretation consistent
with a purposive
construction of the claims in view of the description as a whole.
