Note: Descriptions are shown in the official language in which they were submitted.
6'
DESCRIPTION
~echanical Overspeed Safety Device
TECHNICA~ FIELD
This invention relates to elevators and more
specifically to overspeed governors therefore.
BACKGROUND ART
~ydraulic elevators typically comprise an elevator
car, a sheave, a hydraulic cylinder, and a rope
positioned inside a hoistway. One e~d of the rope is
fixed to the car. From the car, the rope travels upward
in the hoistway to the sheave. The sheave i5 attached
to the rod end of the hydraulic cylinder. The rope
wraps around the sheave and returns back down the
hoistway, attaching at the other end to the bottom of
the hoistway. The hydraulic cylinder propels the car
through the hoistway indirectly by moving the sheave up
and down the hoistway. Since the rope is a finite
length, changing the position of the sheave changes the
position of the car in the hoistway.
For safety reassons, elevators are generally
required to have an overspeed governor and safeties. A
typical overspeed governor includes a governor rope
extending the length of the hoistway r attached to a
sheave at the top of the hoistway and a governor sheave
at the bottom of the hoistway. The governor rope is
fixed to the elevator car by a linkage extending from
the rope to a pair o~ safeties attached to the car.
Because of the fixed relationship, the car and the rope
are normally stationary relative to each other.
With this typP of governor, if the downward
velocity of the elevator exceeds a predeter~sined limit,
i.e~, an overspeed co~ndition, a centrifugal flyweight
~Ex~raàsMair~ be~ _HB350284099.
~ Si~t~J~:o~it October 20, 1992
OT--1396 1 ii~S,~ r~
~__ Sherry B. Holt
20~3~
assembly driven by the governor shsave swings outwardly
and operates a governor brake. The governor brake
applies a frictional drag force to th~ governor rope,
thereby actuating a pair of safeties attached to the
elevator car. The safeties act on a pair of guiderails
and the car is consequently brought to a stop safely.
U.S. Patent No. 3,327,811 to Mastroberte discloses such
an arrangement.
This style overspeed governor, although effective,
protects against overspeed conditions in one direction
only. Specifically, a device like that disclosed by
Mastroberte only works if the rope is traveling in a
downward direction relative to the governor brake which
acts on the rope. To use this type of governor,
therefore, it is necessary to either position the
governor sheave in a room at the top of the hoistway or
to adopt a more elaborate roping scheme which would
allow a Mastroberte type governor ko be implemented in
the pit of the hoistway. Neither of these solutions is
very attractive, however. One of the great advantages
of a hydraulic elevator is that no machine room is
required at the top of the hoistway. Positioning a
governor at the top of the hoistway would eliminate this
advantage. A more elaborate roping scheme, on the other
hand, would require additional sheaves and a longer
rope. These additional items require greater initial
cost, greater maintenance, and more clutter in the
hoistway.
DISCLOSURE OF THE INVENTION
It is thereLore an object of the present invention
to provide a mechanical overspeed device for use in the
pit of an elevator capable of stopping an elevator.
3 ~
According to the present invention, an overspeed
device is provided for an elevator system having an
elevator car or travel withill a hoistway along a
guiderail. The elevator includes a governor rope
running from an upper sheave at the top of the hoistway
to a governor sheave at the bottom of the hoistway. The
overspeed device comprises a centrifugal actuator and a
gripping means. In the event of an overspeed condition,
the actuator actuates the gripping means which in turn
grips the governor rope exiting the governor sheave
upwardly toward the upper sheave. The rope, now moving
relative to the elevator car, operates a safety attached
to the elevator car, thereby safely stopping the car.
An advantage of the present invention is that it
provides a mechanical overspeed device capable of
operating in the pit of a hydraulic elevator with a
roping scheme involving only two sheaves.
These and other objects, features and advantages
of the present invention will become more apparent in
light of the detailed description of the best mode
embodiment thereof, as illustrated in the accompanying
drawings.
BRIEF DESCRIPTION OF THE DR~WINGS
FIG.1 is a diagrammatic view of a hydraulic
elevator with a gvvernor positioned in a hoistway.
FIG~2 shows a centrifugal actuator attached to a
governor sheave, both of which are attached to a
tensioning weight.
FIG.3 is a close up view of the latch shown in
FIG.2.
FIG.3A is a side view of the latch shown in FIG.3.
BEST MODE FOR CARRYI~G OUT THE INVENTION
~ 3 -
2~1136
Referring to FIG.1, an elevator comprises an
elevator car 101, a guiderail 300 a governor sheave 2,
an upper sheave 1, a cylinder sheave 103, a governor
rope 3, and an overspeed device 31 arranged within a
hoistway 32. It is known in the art that there is a
fixed relationship between the elevator car 101 and the
governor sheave 2 such that the linaar motion of the car
101 is translated into rotational motion of the governor
sheave 2. Generally speaking, the fixed relationship is
created by fixedly attaching the elevator car 101 to the
governor rope 3 as is known in the art.
Referring to FIG.2, an overspeed device 31
includes a centrifugal actuator 7 attached to the
governor sheave 2. The actuator 7 has a pair of
identical waights 8,9 rotatably mounted on pins 10,11
which are fixed to the web 33 of the governor sheave 2.
Each pin 10,11 is received by a weight 8,9 in between a
massive portion 8a,9a and an extending arm 8b,9b portion
of the weight 8,9, thereby enabling each portion to
rotate about the pin 10,11. The massive portion 8a,9a
will always be the heavier portion o each weight 8,9.
A spring 15 urges the massive portion 8a of one of the
weights 8 to rotate radially inward about the pin 10. A
flexible contact unit 12 attached to the inner surface
of each massive portion 8a/9a rests against the
rotational axle 13 of the sheave 2. Rotation of the
sheave 2 causes the massive portions 8a,9a to be urged
by centrifugal forces to fly radially outward, against
the urging of the spring 15. A tie rod 14 interconnects
the weights 8,9 forcing them to act in unison.
Referring to FIGS.2, 3 and 3A, a latch 25 is
pivotly pinned to a tensioning weight ~ attached to the
governor sheave 2. The latch 25 is aligned in the
rotational plane of the weights 8,9 mounted on the
3 ~
centrifugal actuator 7. The :Latch 25 consists of a hook
section 25a and a lug section 25b. A pin 34 is received
by the latch 25 in between the hook 25a and lug 25b
sections, thereby enabling the hook 25a and lug 25b
sections to pivot about the pin 340
Referring to FIGo 1, t~e tensioning weight 4
attached to the governor sheave 2 includes a pair of
slides 35 which are shaped to receive a guide 5. The
guide 5, which is attached to the hoistway 32, limits
the motion of the governor sheave 2 and tensioning
weight 4 to vertical motion. The tensioning weight 4
further comprises a tapered section 36 facing the ~uide
5~ A roller 6 is positioned between the tapered surface
36 and the guide 5.
Referring to FIG.2, a gripping means 16 for
gripping the rope 3 in the event of an overspeed
condition is attached to the tensioning weight 4 above
the centrifugal actuator 7. The gripping means 16
includes a stationary jaw 23, a swinging jaw 22, a ~ree
weight 21, and a pair of pivotly mounted links 17,18
connecting the free weight 21 and the swinging jaw 22.
The stationary jaw 23 consists of a brake surface 37, a
pair of pins 38 for holding the brake surface 37 to the
tensioning weight 4, and a spring 24. The pins 38 are
received by a pair of slots 39 in the brake surface 37.
The spring 24 biases the braXe surface 37 in the
~irection of the rope 3 which extends between the
stationary jaw 23 and the swinging jaw 22. During
normal operation, the pins 38 prevent the brake surface
37 from contacting the rope 3. The swinying jaw 22
consists of a bra~e surface 40 pivotly mounted to the
links 17,18 which connect the swinging jaw 22 and the
frPe weight 21. A rod 23a extends out from a side of
the brake surface 40.~ The free weight 21 is also
~$~:~36
pivotly connscted to the links 17,18. On the side of
the governor sheave 2 opposite the stationary jaw 23,
the rope 3 extends through a bore 41 in the cerlter of
the free weight 21. Referring to FIGS.l and 2, in
the operation of a hydraulic elevator having an elevator
car 101 propelled through a hoistway 32 by a hydraulic
cylinder 105, an elevator car rope 102 may break causing
the car 101 to descend at an unsafe speed, whi~h may be
described as an overspeed condition. In the event of an
overspeed condition, i.e. when the rotational speed of
the governor sheave 2 exceeds a predetermined amount,
the pivotally mounted weights 8,9 comprised within the
centrifugal actuator 7 overcome the force of the spring
15 which biases the pivotly mounted weights 8,9 against
the rotational axle 13 of the governor sheave 2. As a
result, the weights 8,9 pivot radially outward and
displace the pivotly mounted latch 25.
During normal operation, the rod 23A ext~nding out
from the swinging jaw 22 is biased against the hook
section 25a of the latch 25 by the free weight 21
attached to the other end o~ the links 17,18. The
swinging jaw 22 is consequent:ly maintained out of
contact with the rope 3. When the lug section 25b of
the latch 25 is struck by the mass.ive portions 8a,9a of
the actuator 7, however, the latch 25 pivots and the
releases the swinging jaw 22. The free weight 21 on the
other end of the links 17,18 drops downward, pivoting
about the pins 19,20 that hold the links 17,18 to the
tensioning weight 4. The swinging jaw 22 attached to
the other end of the links 17,18 is pivoted into contact
with the rope 3 which is traveling upward, away from the
governor sheave 2. The direction of the rope travel and
khe weight of the free weight 21 combine to pivot the
swinging jaw 22 stil~ ~urther, now causing the swinging
-- 6 --
2~8~13~
jaw 22 to displace the rope 3 in the direction of the
stationary jaw 23. The stationary jaw 23, in turn, is
pushed toward the spring 24, thereby compressing the
spring 24. The swinging jaw 22 stops pivoting when it
is aligned with the stationary jaw 23. At that point,
the ~ripping force exerted on the rope 3 by the jaws
22,23 is the force of the spring 24 biasing the
stationary jaw 23 in the direction of the rope 3 and the
now aligned swinging jaw.
As the car 101 continues to descend, the gripping
force on the rope 3 causes the car 101 and the rope 3 to
move relative to one another. Normally, the car 101 and
the rope 3 are stationary relative to one another. As a
result, the linkage 43 attached to the governor rope 3
is dragged upward, away from the elevator car 101.
Dragging the linkage 43 upward causes the linkage 43 to
operate the safeties 42 attached to the elevator car
101, thereby sa~ely stopping the car 101. U.S. Patent
No. 3,327,811 to Mastroberte cliscloses that a linkage
may be attached to a governor rope 3 which actuates a
safety attached to the elevator car 101. The present
invention is directed principally to the overspeed
device claimed.
When the gripping means 16 applies a force to the
rope 3, the weight of the elevator car 101 attached to
the rope 3 on the other side of the sheaves 1,2 will
tend to pick up the governor sheave 2 and tensioning
weight 4. The slides 35 attached to the tensioning
weight 4 and in register with the guide 5 limit thP
movement of the tension weight 4 and governor sheave 2
to up and down in the hoistway 32. The slides 35 and
guide 5 prevent the tension weight 4 from gross movement
which could damage other equipment in the pit 44 ox
cause the governor t~ fail. If the upward movement of
-- 7 --
2 ~
the tensioning weight 4 is too great, the roller 6
positioned between the tapered surface 36 of the
tensioning weight 4 and the guide 5 will bind and
prevent the tensioning weight 4 from traveling further
up the hoistway 32.
Although this invention has been shown and
described with respect to the detailed embodiments
thereof, it will be understood by those skilled in the
art that various changes in form and detail thareof may
be made without departing from the spirit and scope of
the claimed invention.
