Note: Descriptions are shown in the official language in which they were submitted.
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Description
Elevator Brake and Safety
Technical Field
This invention relates to elevators, in
particular, elevator brakes and safeties.
Background of the Invention
In the conventional traction elevator the brake,
which is electromechanically operated, is located in
the machining room, where it is attached to the
drive. As a result, the braking force is limited by
the traction between the cables and the drive. In an
abrupt stop the drive may "slip traction", reducing
the braking force significantly.
The elevator safety, a separate stopping device,
is located on the elevator car. Generally consisting
of a wedge device, a safety rapidly engages the
elevator rail to stop the elevator car. The safeties
are usually progressive; that is, they progressively
reach a maximum tolerable acceleration rate. Safety
operation is typically controlled by an elevator
governor, which, generally speaking, is a mechanical
device that is connected to the elevator car and
which, upon sensing elevator car overspeed, provides
a mechanical pull (actuation) to the safety, causing
it to engage the rail.
OT-550
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Disclosure of the Invention
An object of the present invention is have both
the brake and saEety on the car.
According to the present invention, a brake (e.g.
caliper brake) on the car engages the elevator guide
rail. The brake is mechanically biased to norrnally
freely engage the rail, but the bias is overcome or
prevented by a brake control when braking is not
needed. If overspeed is detected, however, the
operative connection between the brake control and
the brake is interupted, allowing the mechanical bias
to apply the brake.
According to one aspect of the invention, the
bias is overcome by a hydraulic actuator operated by
energizing a solenoid to operate a master cylinder.
The line connecting the master cylinder and the
actuator is vented by another valve when overspeed is
detected, thereby eliminating the need to retract the
master cylinder to apply the brake.
Brief Description of the Drawing
Fig. 1 is a function block diagram of an elevator
according to the invention.
Fig. ? is a function block diagram of a brake
control system according to the in~ention.
' 25 Fig. 3 is plain view of a brake and a rail that
may be used in an elevator embodying the invention.
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sest Mode for Carrylng Out the Invention
In the elevator in Fig" 1, there is a car 10,
counterweight (CW) 12, motor 14, motor control
(MCNTRL) 16 and two guide rails 18. On top of the
car, there is a prime velocity transducer 20, also
called in the art the primary position transducer or
PPT and there is also governor 22. The governor in
this application is connected ~o the velocity
transducer, which, for illustrative purposes, senses
car motion relative to a tape 20a to provide car
velocity output signals. Position and velocity
measurement in that manner is well known. When the
velocity or acceleration or both exceeds
predetermined levels, the governor provides an ES
signal to bring the car to an emergency stop. The ES
signal is supplied to a brake control 28, also on top
of the car. The brake control 28, which is also
connected to the motor control 16 by a traveling
cable 30, controls operation of two brakes 32 and
they are also on top of the car. These brakes engage
the rails, but are maintained in disengagement by the
brake control 28 in response to a brake release (BR)
signal provided from the motor control except when
the car is stopping or is parked, conditions when
braking is neededO
Fig. 2 shows that the brake control 28 contains
an oil tank 29 containing a reservoir of hydraulic
fluid, and a master cylinder (MC) 31 operated by a
solenoid (SOL) 33 which receives the BR signal from
the motor control 16. For illustrative purposes, the
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solenoid has a plunger 33a that controls the position
of the master cylinder. The master cylinder provides
fluid through two lines 31a to the brakes~ each of
which contalns brake shoes 32a that are squeezed
against the guide rails by means of the caliper 32b,
as shown in Fig 3. Each brake contains a spring 40
which expands outwardly so as to force the pads
against the rail, an action by which the brake is
applied. Each brake also contains two separate brake
actuators or cylinders (BC~ 32c on opposite sides of
the spring. When the plunger 33a is moved in one
direction, hydraulic fluid is supplied from the
master cylinder to each brake actuator over one of
the lines 31a, each of which is part of an
independent hydraulic circuit from the master
cylinder. Operation of one actuator therefore will
"release" the brake. The pressure expands the
caliper - overcomes the spring - and thereby
disengaging or releasing the brake pads from the
guide rail. This takes place in response to the BR
signal which causes the solenoid to operate the
master cylinder.
If an overspeed condition occurs, the governor
senses that from the transducer and provides the ES
signal to the brake control. In the brake control
another solenoid 5~ receives the signal and operates
a release valve (RV) 52, and this "vents" the master
cylinder to the tank, (i.e~, releases the pressure in
the lines 31a). The ES signal thus interupts the
operative connection between the master cylinder and
the brake cylinders. Consequently, all pressure from
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brake cylinders 32c is eliminated, allowing the
caliper to close immediately by operation of the
spring, even if the BR signal is still applied.
In lieu of the master brake cylinder, which
provides hydraulic pressure to the brake cylinders, a
hydraulic pump may be used, but with a similar
control that positively releases the brake cylinders.
That is, even iE a configuration like that is
utilized, an electromechanical valve which is
operated independently by the governor should still
be employed to positively release the pressure on the
brake actuators.
Utilizing the foregoin~, one skilled in the art
may make modifications and variations to the
previously described embodiment or embodiments
without departing from the true scope and spirit of
the invention embodied therein.
