Note: Descriptions are shown in the official language in which they were submitted.
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Description
Hydraulic Buffer for Elevators
Technical Field
This invention concerns elevators, specifically,
elevator buffers~
Background Art
Hydraulic buffers are used in elevators to decelerate
the elevator car or the counterweight under certain
conditions. The typical hydraulic buffer has a heavy
fluid container and a piston that extends into this
container to force fluid through the ports. This flow
produces progressive deceleration, and the deceleration
pattern is determined by the location of the ports along
the direction in which the piston moves.
All current hydraulic elevator buffers of this type
use piston seals to clos~ off the space around the piston
rod and the container to prevent entry of contaminating
material, such as dust (which can abrade the piston and
seal surfaces during buffer operations, e.g., during
performance service checks) and to prevent the air/fluid
mixture that results from a buffer operation Erom escaping.
Moreover, the external seals deteriorate over time;
sometimes becoming brittle. Buffer service life is
highly dependent on the eEfectiveness of those piston
seals in blocking contaminants and preventing fluid from
escaping.
Mainly because of the seals, currently available
buffers are comparatively expensive to construct and
expensive and difficult to maintain, and require routine
maintenance to check the sealsO
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Disclosure of Invention
A principal object of the invention is to provide
a very inexpensive buffer that requires no seal inspec-
tion or service.
According to the present invention, a hydraulic
fluid buffer has a piston (plunger) which extends
through a sleeve in the top of a partially filled fluid
(oil) container into an internal cylinder, also partially
filled. When the piston is thrust down, hydraulic fluid
is forced from the cylinder, which produces a fluid/air
mixture within the container as the fluid level rises.
This mixture is forced (by the action of the piston)
through a fluid separator (e.g., a small passage) that
surrounds the piston at the upper portion of the con-
tain~r, and the fluid and air in the mixture separate.The fluid drops out and is directed (e.g., funneled) to
the piston, lubricating the piston as it travels down.
The air is forced out of the container through the sleeve,
removing contaminants, such as dust, from the space
between the piston and the sleeve. As a result of this
configuration, no seals are needed for the purpose of
cleaning the piston or preventing fluid escaping from
the container.
The present invention thus provides a buffer with
a number of features. The buffer has no seals of any
kind; all parts can be metallic. It requires no
maintenance. Buffer test operation removes contaminants
from the space around the piston. Fluid l~vel can be
checked easily, without a dipstick, simply by opening
the port and looking in. If the fluid is not visible,
it is below the minimum; if i~ is visible, it is at
least at the minimum and no greater than the maximum
(i.e., in a safe range).
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A feature of the invention is the buffer may be
easily and economically constructed as a single assembly,
with all parts permanently attached (i.e., welded
together) because no fasteners of any kind need to be
used.
The invention thus offers an exceptionally simple,
inexpensive and virtually maintenance-free buffer.
Brief Description of Drawings
Fig. 1, an elevational view of an hydraulic buffer
according to the present invention, shows the buffer
partially cut away along section line 1-1 in Fig. 2,
exposing its internal components and the fluid;
Fig. 2 is a plan view in the direction 2-2 in
Fig. l; and
Fig. 3 is a magnified view of a portion of Fig. 1.
Best Mode for Carrying Out the Invention
Referring to Fig. 1, a buffer 10 according to the
present invention includes a piston 12 (i.e., a rod)
which extends through a sleeve lOa into a container 16.
Within this container 16b is an internal cylinder 18,
so to speak, which receives the piston and guides it
as it moves in and out of the buffer 10. The piston
has a slightly elevated chamfered portion 12a which
acts as a stop when it engages the portion 16a on the
sleeve. The sleeve extends comparatively tightly around
the piston to provide a good metal-to-metal seal. The
piston 12 also slides tightly within the internal cylinder
18. The cylinder 18 defines a first chamber 19a, a
second chamber l9b outside it, and at the top a collec-
tion area 19c. Both chambers are partially filled with
fluid (oil). There ls a small annular passagP 19d
around the piston at the uppermost part of the cylinder 18
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which separates chambers l9b and l9c, and it acts as a
no~zle to separate oil and air (this is e~plained below~.
The ratio between the height of the passage and its
width (along the circumference of the cylinder 18) is
.013. The ratio of the flow area upstream (below)
the passage to the area at the passage is 120, and the
ratio at the passage to the area downstream (near the
piston) is 13. The passage thus operates as a nozzle.
In addition, the space between the piston and the
slee~e constitutes a second noæzle downstream, through
which air may escape from the container under pressure
therein, and that air must flow from the first nozzle
and, as explained below, cleans the space in the second
nozzle.
The piston 12 contains ring=like cuts l~b along
its lower end, and they pro~ide an hydraulic dynamic
seal without the use of rings, because hydraulic fluid
in these seals is evenly distributed, under even pressure,
around the piston, which helps align the piston and
lubricate it as it moves in the internal cylinder 1~.
(As an alternative, a single metallic piston ring may be
used in the groove urthest from the piston face to limit
the flow past the piston.) Following conventional tech
nology, the cylinder contains por~s 18a along that part
of its vertical length that is within the area immersed
in fluid 20. As the piston strokes down, fluid is
displaced through these ports from chamber 19a to chamber
l9b. The number of remaining ports decreases (this is
not shown) during the downstroke, and thus the flow area
decreases, which increases the resistance to fluid flow
as the piston moves down the cylinder. At the same time,
the piston speed decreases as the ele~ator is decelerated
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and the rate of flow of fluid through the port area
is correspondingly reduced. Thus, the buffer stopping
force remains substantially constant with piston dis-
placement, thus imparting a substantially uniform
deceleration to the elevator. A spring 22 surrounds
the piston 12 and is located at the uppermost portion
of the piston between the cylinder 16 and the striker
plate 24. The spring biases the piston up, holding it
in a position at which the chamfer portion 12a rests
against the lowes~most portion 16c bore 16b. On top
of the plate is a hard rubber block (resembling a hockey
puck) 26, which is contacted by the object, i.e., the
elevator cap or counterweight, to force the piston down
into the cylinder (into the fluid).
A filler hole 26 is located at a special vertical
height 28 on the cylinder. It may have a screw-in cap
and is oriented at a special angle 30 to the horizontal
32. The angle 30, which in the preferred embodiment is
about 20, is such that fluid can be poured into the
cylinder until it reaches a level which corresponds to
the level of the lowest surface 26a on the outermost
portion of the filler hole 26. (If the angle is too high,
air will be trapped inside the cylinder, preventing more
fluid from entering.) The distance 34 between the upper
level U~ and the lower level LL, defined by the lower
surface 26b of the innermost portion of the filler hole,
is the minimum and maximum fluid levels; simply by
looking in the filler hole that can be checked.
During operation of the buffer (as it i5 pushed
down under load) fluid is pushed up in chamber l9b,
and this occurs, as mentioned, through the ports 18a
in the internal cylinder 18. It should not go unnoticed
that this internal cylinder does not extend all the way
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up to the cap; there is that small space l9d between the
lid 16a and the upper portion of the cylinder 18, which
is chamfered (see Fig. 3) around the piston to provide
a fluid funnel around the piston. This configuration
creates a nozæle. As the fluid is pushed up (see arrow
40), a mixture of fluid and air (the bubbles that are
shown) is produced, in the upper area by the fluid
agitation as the fluid rises. This mixture is forced
through the space l9b, and it acts as a noz21e; that
is, agitation and pressure change across the space
cause the air and fluid (oil) to separate, and the fluid
drops down (condenses) in chamber l9c (it acts as a
funnel) around the piston, lubricating the piston as it
mo~es down. The air is forced up under the pressure in
the cylinder and out through the space between the piston
and the sleeve, removing dirt and dust from that space
(it should be as clean as possible). In contrast, other
buffers have seals that are located in the space around
the piston for these cleaning and sealing purposes.
But, the seals deteriorate (as a result of the dirt and
dust which they wipe of and age), and, as a result,
normally have to be replaced from time-to-time~ But,
in this buffer such seals are not present, and hence,
such routine maintenance is unnecessary.
The foregoing demonstrates that by comparison
to current buffers, a buffer embodyin~ the present
invention is ver~ simple and reliable, inexpensive
and easy to maintain.
The foregoing descrip-~ion of a buffer embodying
the present invention ~ill suggest, to one skilled
in the art, various modifications and alterations,
without departing from the true scope and spirit of
the invention.
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