Note: Descriptions are shown in the official language in which they were submitted.
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WO 97/12829 PCTIUS96/15901
_ ELEVATOR STOPPING DEVICE
TECHNICAL FIELD
The present invention relates generally to safety brakes for hydraulic jacks
or rams. In
particular, the present invention relates to a hydraulic ram lifting elevator
emergency arrestor using
a lever and lock mechanism to provide braking action without permanently
damaging or
destroying the hydraulic ram.
BACKGROUND ART
The present invention relates to a hydraulic ram arrestor using a lever lock
type of
mechanism which is activated by a pressure failure condition, down overspeed,
or uncontrolled
down motion. When activated; two lever acting brake amps are dropped into
contact with the
elevator ram, the resulting friction bringing the elevator to a sliding stop.
There have been numerous brake systems developed for stopping hydraulic ram
elevators
during emergency situ;~tions. All of the prior art patents found were directed
toward collets or
brake shoes, that, during a hydraulic pressure failure, would drop down and
wedge in between a
fixed housing and the ram of the elevator. The friction generated by the
downward motion of the
ram in contact with the: collet or brake shoe causes the collet or brake shoe
to be driven
downwardly, thereby wedging the ram to a halt. Empirical evidence indicates
that the force
necessary to stop an elevator using such a brake exceeds the elastic limit of
the material used in
commercial rams causing the ram to be permanently deformed into an hourglass
shape at the
point where such brakes grip the ram. The prior art elevator safety brakes
have no positive stop to
limit the deformation to the elevator ram caused by the braking mechanism.
This type of damage
to the ram cannot be repaired and instead, expensive and time consuming
replacement is required
to restore the elevator to working condition. The prior art patents also
disclosed elevator brakes
that have many moving parts, and are correspondingly complex. Additionally,
the prior art
devices appear relatively large and bulky. Size is an important consideration
because there is often
limited space into which to fit a braking device. Therefore, it is desirable
for the brake to have a
low profile, thereby facilitating installation in all present hydraulic
elevators.
As a specific example of a prior art design having the above mentioned short
comings,
Beath et al., patent ##4;449,615 is a floor mounted lever-actuated wedge
device. The many
components in this design complicate it by comparison to the present
invention. Beath uses
collets, that, during a hydraulic pressure failure, drop down and wedge in
between a fixed housing
and the ram of the elevator. The friction generated by the downward motion of
the ram in contact
with the collets causes the collets to be driven downward, thereby wedging the
ram to a halt. The
force necessary to stop an elevator using the brake disclosed in Beath exceeds
the elastic limit of
the material used in commercial rams causing the ram to be permanently
deformed into an
hourglass shape at the point where the collets grip the ram. Additionally, the
above mentioned
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CA 02233957 2004-03-19
patent does not precisely show relation to the top of the cylinder and the
bottom of the
elevator. However, it appears too tall to fit most existing elevator systems.
In light of the problems listed above and exemplified by patent #4,449,615, a
new
elevator brake is needed that can safely stop a fixlly loaded elevator without
permanently
damaging the ram.
The present invention, using an accretable metal or other adherent material to
apply
a braking force to the ram is a clear improvement over the prior art.
Prototype testing has
shown that copper bar formed to shape has yielded sufficiently high braking
force, with and
without the presence of oil on the surface of the ram. Several materials have
been tested,
and, to date, copper has been the best material for the purpose. The present
invention is
also comparatively simple and low in profile facilitating installation on
current elevator
designs.
SUMMARY OF THE INVENTION
It is a feature of preferred embodiments of the present invention to provide a
mechanism for arresting an elevator which can safely stop a fully loaded
elevator without
permanently damaging any part of the elevator.
It is another feature of the present invention to provide, in preferred
embodiments,
an elevator arrestor that allows the elevator to be usable within a short
period of time with
little reset and repair necessary. Optimally, the reset and repair should be a
relatively
simple and inexpensive procedure.
It is a fixrther feature of the present invention to provide an arrestor,
which in
preferred embodiments, will fit within a small vertical space such that it can
fit within the
normal design parameters for hydraulic ram elevators, and may also be retrofit
into existing
hydraulic ram elevators.
It is yet another feature of a preferred embodiment of the present invention
to
provide a system that can be easily installed and requires very little down
time in which the
elevator is non-functional.
It is an additional feature of the present invention to provide for an
arresting system
that is inexpensive to manufacture.
In accordance with one embodiment of the present invention there is provided
an
arresting device for halting relative motion between a main cylinder and a
second cylinder
of a hydraulic elevator, wherein the second cylinder moves within the main
cylinder,
wherein the second cylinder has a perimeter and an external radius of
curvature. The
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CA 02233957 2004-03-19
arresting device comprises: two lever arms, each of the two lever arms having
an
approximately semi-cylindrical braking surface and a pivot point, the
approximately semi-
cylindrical braking surface having an internal radius of curvature which is
smaller than the
external radius of curvature of the second cylinder, and the pivot point being
offset from
the braking surface. The lever arms have a first position wherein the lever
arms are capable
of being rotated away from the second cylinder with the braking surface out of
contact with
the perimeter of the second cylinder, and a second position wherein the lever
arms are
capable of pressing the braking surface against the perimeter of the second
cylinder to
generate a braking force.
In accordance with another embodiment of the present invention there is
provided
an arresting device for halting relative axial motion between a hydraulic
cylinder and a ram
of a hydraulic elevator, wherein the ram moves within the hydraulic cylinder
and wherein
the ram has an exterior surface and an external radius of curvature. The
arresting device
comprising: two lever arms, each of the two lever arms having an approximately
semi-
cylindrical braking surface and a pivot point, the approximately semi-
cylindrical braking
surface having an internal radius of curvature which is smaller than the
external radius of
curvature of the ram, and the pivot point being offset from the braking
surface. The lever
arms have a first position wherein the lever arms are capable of being rotated
away from
the ram, and a second position wherein the lever arms are capable of pressing
the braking
surface against the exterior surface of the ram to generate a braking force. A
detection
system is provided for detecting an emergency situation, the detection system
being in
communication with the lever arms, whereby when the detection system detects
an
emergency situation the lever arms is moved from said first position to the
second position.
In accordance with yet another embodiment of the present invention there is
provided a hydraulic elevator safety system comprising: a hydraulic elevator
having a lifting
ram cylinder, the ram cylinder having a perimeter having an external radius of
curvature,
and an elevator safety brake having a first lever arm and a second lever arm.
Each lever
arm has a pivot point and an approximately semi-cylindrical braking surface,
the
approximately semi-cylindrical braking surface having an internal radius of
curvature that is
smaller than the external radius of curvature of the ram cylinder, and the
pivot point being
offset from the braking surface. The first and second lever arms having a
first position
wherein the lever arms are rotated away from the ram cylinder with the braking
surfaces
out of contact with the perimeter of the ram cylinder, and a second position
wherein the
lever arms press the braking surfaces against the perimeter of the ram
cylinder to generate a
braking force.
CA 02233957 2004-03-19
In accordance with a further embodiment of the present invention there is
provided
a hydraulic elevator safety system comprising: a hydraulic elevator having a
lifting ram
cylinder, the ram cylinder having a perimeter having an external radius of
curvature, and a
first lever arm and a second lever arm, each having a pivot point and an
approximately
semi-cylindrical braking surface having an internal radius of curvature that
is smaller than
the external radius of the ram cylinder. The braking surfaces comprise
annealed copper.
The pivot point is oi~set from the braking surface. The first and second lever
arms have a
first position wherein the lever arms are rotated away from the ram cylinder
with the
braking surfaces out of contact with the perimeter of the ram cylinder, and a
second
position wherein the lever arms press the braking surfaces against the
perimeter of the ram
cylinder to generate a braking force. A pair of side buttress members are
provided, the first
and second lever arms being pivotally attached to the side buttress members at
the pivot
point. A base plate is provided, the base plate located below the first and
second lever
arms. When the first and second lever arms are in the second position, the
lever arms are,
parallel to and in contact with the base plate. A detection system is provided
for detecting
an emergency situation, the detection system being in communication with an
actuation
means for moving the first and second lever arms from the first position to
the second
position when the detection system detects the emergency situation.
In accordance with a still further embodiment of the present invention there
is
provided a hydraulic elevator safety system comprising: a hydraulic elevator
having a lifting
ram cylinder, the ram cylinder having a perimeter having an external radius of
curvature,
and a first lever arm and a second lever arm, each having a length, a first
end and a second
end, and an approximately semi-cylindrical cut-out for receiving an
approximately semi-
cylindrical braking surface. The approximately semi-cylindrical braking
surface having an
internal radius of curvature that is smaller than the external radius of the
ram cylinder. The
braking surfaces comprising annealed copper. The first and second lever arms
are pivotable
along a pivot axis that is oi~set from the braking surface, the first and
second lever arms
having a first position wherein the lever arms are rotated axially around said
pivot axis
away from the ram cylinder with the braking surfaces out of contact with the
perimeter of
the ram cylinder, and a second position wherein the lever arms press the
braking surfaces
against the perimeter of the ram cylinder to generate a braking force. A first
pivot pin is
coupled to the first end of the first lever arm in alignment with the pivot
axis, and a second
pivot pin is coupled to the second end of the second lever arm in alignment
with the pivot
axis. A pair of side buttress members are provided, having pivot apertures,
the pivot pins
of the first and second lever arms being received within the pivot apertures
of the side
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CA 02233957 2004-03-19
buttress members. A base plate is located below the first and second lever
arms. When the
first and second lever arms are in the second position, the lever arms are
parallel to and in
contact with the base plate. A detection system detects an emergency
situation, the
detection system being in communication with an actuation means for moving the
first and
second lever arms from the first position to the second position when the
detection system
detects the emergency situation. A hydraulic actuation assembly is provided
for actuating
the elevator safety system coupled to the detection system. A support
structure comprises
a plurality of support legs, each support leg being coupled at a first end to
an upper cup,
each upper cup being coupled to the base plate, each support leg being coupled
at a second
end to a lower cup, each lower cup being coupled to support tubes.
The present invention is a hydraulic safety arrestor for slowing and stopping
a ram,
jack or other cylinder type object. In preferred embodiments, it utilizes two
lever acting
brake arms lined with an accretable metal as the friction material. When
actuated, the brake
arms contact the ram circumferentially and press the fi-iction material
against the surface of
the ram to slow and stop the falling ram. The lining material is machined
inside the brake
arms to a diameter slightly less than the diameter of the ram. When actuated,
the lining
material contacts the ram with sufficient frictional force to stop the
downward motion of
the ram without permanent deformation of the ram. The force applied to the
surface of the
ram by the brake arms causes a temporary hourglass deformation of the ram
which greatly
augments the friction force to retard the falling ram. The geometry of the
braking
mechanism limits the deformation to well within the elastic limit of the ram
material to
prevent any permanent deformation to the ram. The rest of the mechanism is
comprised of
side buttress members, pivot pins, and a base plate, mounted above a spacer
ring. The
spacer ring is the same diameter as the cylinder and is variable in length to
raise the base
plate and brake assembly above any bolts or other existing projections.
Eyelets are welded
to the existing cylinder to provide for secure mounting and correct alignment
and
realignment when the brake is removed and reinstalled.
The brake arms may be actuated mechanically by loss of hydraulic pressure, by
an
electronic signal from a hydraulic pressure detector, by down overspeed or by
an
uncontrolled down motion detector.
The force applied by the braking action is transferred from the brake arms
through
the base plate and spacer ring onto the circumferential area of the top of the
main cylinder
and any associated support structures. By monitoring the pressure and
overspeed, the fall
of the elevator can be limited to speeds with a maximum of less than twice the
normal
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CA 02233957 2004-03-19
down speed, thus limiting the kinetic energy produced, by not allowing a free
falling
elevator. Therefore, the pit structure would absorb the energy without damage
or
deformation, without any modifications to the pit structure.
These and other features and advantages of the invention will no doubt occur
to
those skilled in the art upon reading and understanding the following detailed
description
along with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side elevation view showing the brake and control components
according
to the invention;
Fig. 2 is the front elevation view showing the brake and control components
according to the invention;
Fig. 3 is a sectional view showing the frictional contact, and locations of
the
packing in relation to the invention, as viewed along the line 3-3 in Fig. 4;
Fig. 4 is a plan view of the invention;
Fig. 5 is a sectional view of an alternate embodiment of the brake according
to the
invention;
Fig. 6 is a plan view of an alternate embodiment of the brake of the present
invention having multiple brake arms;
Fig. 7 is a plan view of the brake of the present invention having an
alternate
embodiment of the hinge mechanism;
Fig. 8 is a sectional view of the brake of Fig. 7 taken along line 8-8 to show
the
alternate embodiment of the hinge mechanism; and
Fig. 9 shows an alternate mounting arrangement for the brake system which
transfers the braking force directly to the floor of the elevator shaft.
DETAILED DESCRIPTION OF THE INVENTION
The drawings show a safety brake system according to the present invention,
indicated generally by the reference number 1. Although the brake system 1 is
applicable to
many hydraulic
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WO 97/12829 CA 02233957 1998-04-03 PCTlUS9ft/15901
ram or piston devices, it is described here in its preferred use on a
hydraulic ram lifting elevator.
References to "up", "down", "vertical", "horizontal", etc. should be
understood to refer generally
to the relative positions of the components of the illustrated device, which
could be otherwise
oriented or positioned for non-elevator applications. Although the term
"hydraulic" is used,
references to "hydraulic" should be understood to refer generally to any
pressure ram device with
a main cylinder which surrounds a second, axially-moving cylinder or ram,
including but not
limited to hydraulic and pneumatic ram devices. In addition, the present
invention can be used as a
brake on any linear motion c~vice with an axially-moving compression or
tensile member.
In Fig. 1, a reciprocating piston or ram 3 is shown with brake system I
installed on the
existing main cylinder S of a hydraulic elevator. The ram 3 of a hydraulic
elevator is typically a
hollow steel cylinder with a smoothly ground exterior surface. The external
diameter of a
hydraulic elevator ram 3 is typically in the range of approximately 3.5 inches
to 8 inches, although
some hydraulic elevator rams are as large as 15 inches in diameter. The wall
thickness of the
hydraulic elevator ram 3 is nominally 0.250 inches, with a range from
approximately 0.18$
inches to approximately 0.375 inches, depending on the external diameter of
the ram 3. Spacer
ring 7 rests upon the upper end of main cylinder 5 at 9 and is removably fixed
to upper end of
main cylinder 5 by any one of a number of known fastening means. Tn a
preferred embodiment,
the known fastening means comprises eyelets 11 fixed to the outside surface of
main cylinder S
and near the upper end 9 of main cylinder S. Each eyelet comprises a pair of
flanges 15 spaced a
short distance apart, and flanges 17 on spacer ring 7 fit in between flanges
15 of eyelets 11.
Flanges 17 and flanges 15 have bolt holes 19 which are aligned to accept
eyelet bolts 20 to fix
spacer ring 7 to main cylinder 5. In an alternate embodiment, eyelets 11 may
comprise only a
single flange. The advantage of using eyelets 11 is that any one of eyelets 11
can act as a pivot to
rotate brake system 1 away from main cylinder 5 to allow access for servicing
when eyelet bolts
20 are removed from the other eyelets 11. Removal of all eyelet bolts would
allow total removal
of brake system 1 for major work. Eyelets 11 also allow for exact reattachment
of the device
assuring proper alignment. Base plate 21 is fixed to the upper surface of
spacer ring 7 at 23. Side
buttress members 25 are fixed to base plate 21 on either side of brake arms
27. In the preferred
embodiment, brake arms 27 are hingably fixed to side buttress members 25 by
pivot bolts 29
allowing brake arms 27 to rotate into or out of contact with ram 3.
When the hydraulic elevator safety brake is in the ready or standby position,
as shown in
Fig. 2, brake arms 27 are raised approximately 15 degrees from horizontal,
allowing travel
clearance for ram 3. Brake arms 27 are shaped having semicircular cut-outs 26,
which are best
seen in plan view in Fig. 4, of diameter slightly larger than ram 3, and
having a fi-iction material
mounting surface 28 on the inside of cutouts 26. An accretable friction
material 3I is fixed to the
friction material mounting surfaces 28 of semicircular cut-outs 26 of brake
arms 27. The
accretable friction material 31 rests on a small shelf or ledge 67 which
extends from the friction
material mounting surface 28 on the inside of cutouts 26, as seen in cross
section in Fig. 3. In one
particularly preferred embodiment of the invention, the ledge 67 and the
friction material
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WO 97/12829 PCT/US96/15901
mounting surface 28 are machined into semicircular inserts 85 which are bolted
86 into the
semicircular cut-outs 26 of brake anus 27. This arrangement simplifies the
machining operations
of the brake arms 27 and provides an easy means for replacing the friction
material 31 in the field.
An accretable friction material is a material which causes friction by
adhesion of the friction
material to the moving surface which it contacts. The braking mechanism may
also involve actual
material transfer or "accretion" of the accretable friction material onto the
moving surface. In a
preferred embodiment the accretable material 31 is annealed copper, but other
materials may be
used. Annealed copper is preferred because, of all the materials tested, it
has the greatest tendency
to adhere to the ram 3. This maximizes the amount of friction between the ram
3 and the brake
lining 31, which creates the greatest braking force with the least amount of
damage/deforrnation
of the ram 3 and the braking system 1. The inside diameter of the accretable
friction material 3I is
slightly smaller than the outside diameter of the ram 3. This provides proper
frictional
engagement with ram 3 to bring the elevator to a halt.
Fig. 3 shows the brake system 1 in the actuated position with the brake arms
27
approximately perpendicular to the surface of the ram 3 and the accretable
friction material 31 in
circumferential contact with the ram 3. Further travel downward by brake arms
27 is prevented by
contact with base plate 2I. Spacer ring 7 transfers the braking force from the
brake arms 27 and
base plate 21 onto the main cylinder 5 or any associated support structure
which may exist.
Eyelets 11 and the structural strength of spacer ring 7 prevent brake system 1
from slipping and
assure equal transfer of force directly downward, into existing main cylinder
5 or onto any
associated cylinder support structures. Kinetic energies can be limited by
limiting the down speed
allowed before brake system 1 is actuated, thereby preventing damage to the
brake system 1, ram
3 or to the main cylinder 5.
The braking force from the hydraulic elevator safety brake is provided by two
cooperative
braking mechanisms. The primary braking mechanism is from the frictional force
between the
friction material 3I and the surface of the ram 3. This frictional force is
maximized by the use of
an accretable friction material 3I, such as annealed copper. The frictional
force between the
accretable friction material 31 and the surface of the ram 3 is further
augmented by a second
braking mechanism. When the brake arms 27 are in the actuated position, as
shown in Fig. 3, the
interference fit between the inner diameter of the friction material 31 which
forms the braking
surface and the outer diameter of the ram 3 causes a temporary hourglass
deformation of the ram
3. This elastic deformation of the ram 3 as it passes between the actuated
brake arms 27 absorbs
much of the kinetic energy of the falling elevator, helping to safely bring
the elevator to a stop.
This secondary braking mechanism, which greatly augments the frictional force
of the braking
system, is particularly important in situations where the elevator ram 3 or
the friction material 31
becomes contaminated with hydraulic fluid or lubricating oil, interfering with
the primary
frictional braking mechanism. Unlike the collet-type elevator safety brakes of
the prior art, the
geometry of the brake arms 27 in the present invention limits the deformation
to well within the
elastic limit of the ram material to prevent any permanent deformation to the
ram 3. The hourglass
S
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W097/12829 CA 02233957 1998-04-03 P~T/US9ø/15901
deformation of the ram 3 has been exaggerated in Fig. 3 for illustrative
purposes. Testing of the
braking system has shown that an interference fit of approximately O.OIO
inches to approximately
0.020 inches between the inner diameter of the braking surface of the friction
material 31 and the
outer diameter of the ram 3 in the actuated position is sufficient to reliably
stop a loaded elevator
weighing from 4,000 to 12,000 pounds, even when the ram 3 is contaminated with
hydraulic
fluid or lubricating oil.
To account for variations in manufacturing tolerances or for wear of the
friction material
31, stems 68 may be added between the friction material mounting surfaces 28
and the friction
material 31 to adjust the interference fit. Shims 68 of this sort may be used
in the field at the time
of installation or during peri~dic maintenance for adjusting the stopping
force of the braking
system. For safety reasons, it is preferable that the elevator safety brake
bring the elevator car to a
stop with a deceleration of approximately 0.5 to 1.0 g's. Knowing the top
speed of the elevator,
the corresponding braking distance can be calculated. for example, for an
elevator with a top
speed of 200 feet per minutes a 0.5 to 1.0 g deceleration would correspond to
a stopping distance
between approximately 4.2 and 2.1 inches. By trial and error, the elevator
installer or adjuster adds
shims until the braking system stops a loaded elevator with a braking distance
within the
calculated range.
In the preferred embodiment, brake system 1 is actuated by loss of hydraulic
pressure
detected by direct feedback from the main cylinder 5, by an electronic signal
indicating loss of
pressure in the cylinder 5, by electronic signal from a down overspeed, or by
an uncontrolled
down motion detector. Brake system 1 is actuated by downward motion of
actuation rod 35
attached to the actuation assembly, generally identified by 33. The top of the
actuation rod 35 has a
circular or rectangular shaped metal wafer 37 that is received inside shaped
hollows or routs 39 in
the brake arms 27. This assures registration between both brake arms 27.
Hydraulic actuation of brake arms 27 is accomplished by the hydraulic
actuation
assembly, generally referenced by the number 38. The hydraulic actuation
assembly 38 is located
in and around feedback control cylinder 43 which is fixed between upper
hydraulic cylinder
bracket arrn 46 and lower hydraulic cylinder bracket arm 48 of hydraulic
cylinder bracket 55, both
bracket arms 46, 48 being fixed to hydraulic cylinder bracket 55. The
hydraulic actuation
assembly 38 comprises feedback cylinder 43 having portal 41 to receive the
lower end 46 of
actuation rod 35, plunger 47 fixed to the lower end 46 of actuation rod 47,
and helical
compression spring 45 which is engaged over and around the lower end 47 of
actuation rod 35,
one end of compression spring 45 engaging the inside surface of the top of
feedback cylinder 43
and the other end engaging plunger 47. hlelical compression return spring 45
urges plunger 47,
and actuation rod 35 fixed thereto, downward. Under normal conditions,
hydraulic pressure in
feedback cylinder 43, in fluid communication with main cylinder 5, overcomes
the compressed
spring energy of return spring 45, urging plunger 47 upward, which in turn
urges control rod 35
upward, which then urges brake arms 27 into ready or standby position.
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WO 97/12829 PCT/US96/159ot
Loss of hydraulic pressure in the main cylinder 5, is communicated to feedback
cylinder
43 through hose 49 (Figs. I and 2). Return spring 45 overcomes the reduced
pressure in feedback
cylinder 43 urging plunger 47 and attached actuation rod 35 downward pulling
brake arms 27 into
contact with ram 3. Friction resulting from contact of accretable material 31
on the friction
material mounting surface 28 of brake arms 27 urges drake arms 27 further
downward into
contact with ram 3 until brake arms 27 rest on horizontal base plate 2I. The
accretable friction
material 31 on brake arms 27 grips ram 3 with sufficie~tt frictional force to
stop the downward
motion of ram 3.
Electronic actuation of brake arms 27 is accomplished by the electronic
control assembly
generally referenced by the number 40 comprising control bracket 57 fixed to
spacer ring 7, upper
solenoid bracket arm 61, and lower solenoid bracket arm 63, both being fixed
to control bracket
57. Electronic actuation assembly 40 further comprises, electronic activator
rod 59, and helical
compression support spring 51 placed over and around electronic actuation
control rod 59, the
upper end of support spring 51 engaging lower surface of hydraulic control
assembly 38, and the
lower end of support spring 51 engaging the upper surface 51 of solenoid
bracket 61.
In the preferred embodiment, electronic activator rod 59 is fixed at its upper
end,
generally, to the hydraulic actuation assembly 38, which is slidably engaged
with slide bracket 44,
slide bracket 44 being fixed to control bracket 57. Solenoid helical
compression support spring
51, is selected to support the weight of brake arms 27 and hydraulic actuation
assembly 38.
Tubu~iar solenoid 65 is fixed between upper and lower solenoid bracket arms 61
and 63. The
lower end of electronic actuation rod 59 partially penetrates tubular solenoid
65. The upper end of
electronic actuation rod 59 is coupled to the underside of lower hydraulic
cylinder bracket arm 48
of hydraulic cylinder bracket 55. An electronic signal from a down overspeed
detector or
uncontrolled downward motion detector, not shown, causes an electric current
in solenoid 65
generating a magnetic field of strength sufficient to urge electronic
actuation rod 59 downward
into tubular solenoid 65, thereby pulling the entire hydraulic actuation
assembly 38, slidably
engaged to slide bracket 44, downward thereby actuating brake arms 31.
In an alternate embodiment, the electrical actuation assembly 40 can be used
to actuate the
hydraulic elevator safeay brake directly without inclusion of the hydraulic
actuation assembly 38.
In this alternate embodiment, the electrical actuation assembly 40, which is
otherwise the same as
described above, has the electronic actuation rod 59 engaged directly with
brake arms 27. To
replace the function of the hydraulic actuation assembly 38 in this
embodiment, an electronic
signal from a hydraulic pressure detector within the main cylinder 5 could
also be used to actuate
the electronic actuation assembly 40, in addition to a down overspeed or
uncontrolled downward
motion detector.
A variety of known down overspeed or uncontrolled downward motion detectors
are
available for use with this invention. For example, devices such as those
disclosed in Coy, Patent
No. 4,638,888 which discloses an electronic system for detecting the hydraulic
pressure in an
elevator ram piston cylinder, and Ericson, Patent No. 5,052,523 and Sobat,
patent no. 3,942,607,
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WO 97/12829 PCT/US96115901
which both disclose mechanical means for detecting the downward speed of an
elevator.
Given the generally small distance from the bottom of a standard hydraulic
lift elevator to
the top of the existing piston cylinder structure, a low profile device is
desirable. The present
device, in ready position is between four and five inches high. This is
accomplished by keeping
the fulcrum angle at 15 degrees as shown in the drawings, best seen in Figs. 1
and 2. Therefore, it
is easily mounted onto all existing elevator cylinders.
Packing 16 is shown in Fig. 3 for illustrative purposes only, and vanes from
elevator to
elevator depending on the manufacturer. The length of spacer ring 7 is
dependent on the packing
mechanism used by the various makes.
In general, the packing of all rams is located in the cylinder head at the top
of the cylinder.
The packing is the seal which retains the oil pressure and allows the smooth
ram wall to slide
relatively freely through it. Generally, there is some bypass of oil through
this seal. When this
bypassed oil is excessive it is customary to change the packing. As common as
this procedure is,
it is desirable to allow easy and open access to the cylinder head. As
explained previously, the
present invention utilizes a three point eyelet mounting. Any one of eyelets
11 can act as a pivot to
rotate brake system 1 away from main cylinder 5 to allow access for servicing.
By assuring
enough range of motion by having a feedback hose 49 and electrical wiring of
sufficient length,
the device is easily rotated for access to packing 16 without the need to
disconnect electrical wiring
or hydraulic connections.
National, state and local codes provide regulations for periodic testing of
safety devices, so
it is desirable to retest without damaging either the ram or the brake.
Prototype testing to date has
shown less than twenty thousandths of an inch deformation of the annealed
copper at the open
edges of the annealed copper bar, where the brakes meet centrally when closed,
and no
deformation elsewhere. Thus periodic testing is available, and the common
practice of blocking
the elevator to serve as a stable working platform is easily done by manually
setting the brake.
Although the previously described embodiment of the hydraulic elevator safety
brake uses
two brake arms, a multiplicity of brake arms could be also used. Fig. 6 shows
an exemplary
embodiment of the hydraulic elevator safety brake 70 of the present invention
having a
multiplicity of brake arms 72. In this illustrative example, the hydraulic
elevator safety brake 70
has three brake arms 72. Each of the brake arms 72 has a braking surface 71
which represents a
segment of a circle so that the braking surfaces 71 totally encircle the ram 3
when combined
together. Each of the brake arms 72 is pivotally mounted by a hinge bolt 73 to
side buttress
members 74, which in turn are bolted to a mounting plate 75 which attaches to
the head of the
main cylinder 5 of the hydraulic elevator. As in the previously described
embodiment, the braking
surfaces 71 have an inner radius of curvature which is slightly less than the
external radius of
curvature of the ram 3, so that, when the brake arms 72 are in the actuated
position, the combined
braking surfaces 71 define a circle with an inner diameter which is slightly
smaller than the
external diameter of the ram 3. In other embodiments of the invention, the
hydraulic elevator
8
,- .... ~. ' CA 02233957 1998-04-03__. _ .," ......",..".,.~..____.-__._
WO 97/12829 PCT/US96/15901
safety brake may have four or more brake arms each carrying a section of the
braking surface.
These sections could be equal in size, or they could be disparate, if desired.
Different sized
sections could be advantageous in some situations, including where the
configuration of the work
space makes installatian or maintenance easier if a certain portion of the
brake system is more
articulated.
In an alternate brake arm embodiment, shown in Fig. 5, cutting bits or teeth
66 may be
fixed to the friction material mounting surface 28 of brake ands 27 in place
of or in addition to
accretable friction material 31. In this alternate embodiment, braking is
accomplished by the teeth
66 biting into ram 3. Unlike the hourglass damage caused by the prior art, the
type of damage
caused by this alternate embodiment can be repaired by filling and filing the
gouges.
Other systems for hingably mounting the brake arms 27 are possible. An
embodiment of
the hydraulic elevator safety brake having an alternate hinge mechanism is
shown in plan view in
Fig. 7 and in cross section in Fig. 8. In this alternate er~tbodiment, the
brake arnls 27 are pivotally
mounted between back buttress members 80 which are mounted on the base plate
21. The back
buttress members 80 have a concave channel 81 which pivotally receives the
rear edge 82 of the
brake arms 27. The rear edges of the brake arms 27 are rounded to fit the
concave channel 81 of
back buttress members 80. During pivotal movement of brake amls 27, the
rounded rear edges
82 of brake arms 27 slide within the concave channels 81 of back buttress
members 80. When the
brake arms 27 are in the actuated position, the braking force from the braking
surface 31 is
transferred through the brake arms 27 to the back buttress members 80.
Optionally, side buttress
members 83 may be provided to reinforce the back buttress members 80 and to
reduce
deformation under load. Hinge bolts 84 may also be provided to pivotally
attach the brake arms
27 to the side buttress members 83, however, in this embodiment the greater
portion of the load is
preferably borne by the back buttress members 80 and rather than by the hinge
bolts 84.
Fig. 9 shows an alternate mounting arrangement 90 for the brake system 1 which
transfers the braking force generated by the brake system 1 directly to the
floor of the elevator
shaft rather dean to the main cylinder 5 of the elevator. The base plate 21 of
the brake system 1 is
mounted on four support legs 91 which extend downward toward the floor of the
elevator shaft.
Upper cup-shaped members 95 attach the upper ends of the support legs 91 to
the base plate 21.
The lower ends of the support legs 91 are attached by lower cup-shaped members
94 to support
tubes 93 which distribute the braking force evenly across the footer channels
92 which rest on the
floor of the elevator shaft. Additional reinforcing members 99 may be provided
to rigidify the
structure. The lengths of the support legs 91 may be individually adjusted by
adding shims to the
upper or lower ends of the support legs 91 to level the brake system 1.
Braking force generated by
the brake system I is 'transferred through the support legs 91 to the footer
channels 92, then to the
floor of the elevator shaft.
Fig. 9 also shaves an alternate control system for the brake system I having a
hydraulic
control cylinder 98 which is operated by a solenoid-actuated three-way valve
96. During normal
operation of the elevator, the solenoid-actuated three-way valve 96 is open
and hydraulic pressure
9
W097/12829 CA 02233957 1998-04-03 PCT/US96/,15901
within the hydraulic control cylinder 98 holds the brake system 1 in the ready
position. In the
event of an emergency situation, such as loss of hydraulic pressure, down
overspeed or an
uncontrolled downward motion of the elevator, a control signal causes solenoid-
actuated three-
way valve 96 to close so that a return spring within the hydraulic control
cylinder 98 moves the
brake system 1 into the actuated position to halt the downward motion of the
elevator. This
control system is also designzd so that if there is a complete loss of either
hydraulic pressure or
electrical power, the return spring within the hydraulic control cylinder 98
will actuate the brake
system 1 and halt the motion of the elevator.
The configuration of the hydraulic elevator safety brake of the present
invention makes it
ideally suited for retrofitting onto existing hydraulic elevators. The use of
two or more pivoting
brake arms which surround the elevator ram allows the safety brake to be
assembled around the
ram, with no need to remove the ram or to detach it from the elevator car.
Prior art elevator safety
brakes which use a circular collet in the brake mechanism cannot be installed
onto existing
elevators without removing or detaching the elevator ram. This severely limits
their usefulness as
a retrofit safety device for existing elevators. Alternatively, the hydraulic
elevator safety brake of
the present invention can also be built into new elevator installations as
standard equipment. In
these cases, the safety brake mechanism can be integrated into a single unit
with the head of the
main cylinder of the elevator.
In addition to hydraulic elevators, the elevator safety brake 1 of the present
invention can
also be configured for use as a safety brake for cable-actuated traction
elevators. For use in this
application, the ram 3 in each of the foregoing drawing figures would be
replaced with the traction
cable (or cables) of the cable-actuated elevator. The braking surface 31 of
the brake arms 27
would be configured to frictionally engage the cable or cables of the elevator
when the brake arms
27 are in the actuated position. Thus, when it is mounted in the orientation
shown in the drawing
figures, the brake 1 can be used to stop a falling traction elevator. The
brake 1 can also be
mounted in an inverted orientation for use as a safety brake to stop an
uncontrolled ascent of a
cable-actuated traction elevator, a phenomenon known in the elevator industry
as "falling up".
SUBSTITUTE SHEET (RULE 26)
