Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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WINCH SAFETY CONTROL
BACKGROUND_OF THE INVENTION
This invention pertains to fluid actuated multi-speed motors with
electronic pressure sensitive override controls and more specifically to
a hydrostatic motor for a two-speed winch which is hydraulically actuated
to shift from one speed ratio to another.
It has been recognized in the prior art that it would be desirable
to have an override system to shift a hydraulically actuated multi-speed
ratio motor to a lower speed ratio when pressure in the hydraulically
actuated con~rols reaches a certain predetermined level. However, in
the prior art known to the inventor attempts to provide a hydraulic
override system were not satisfactory because the hydraulically actuated
controls constantly shifted or hunted between speed ratios at certain
line pressures. Therefore, most hydraulically actuated motor controls
of the prior art did not employ an override system but relied on safety
check valves to open and lower hydraulic pressure in the hydraulically
actuated controls when the hydraulic pressure reached a predetermined
unsafe level. A major disadvantage in the prior art hydraulic system is
that the motor is completely shut down at high hydraulic pressures. In
motors for crane winches a shutdown could result in loads being sus-
pended in mid-air until the motor is reset.
This invention solves the previously mentioned problems and dis-
advantages of the prior art by providing low and high speed ports in the
motor corresponding to low and high speed ratios and a port conduit
extending from each respective port. A valve operatively connected with
both conduits can be selectively positioned to supply fluid under
pressure to a selective one of the port conduits so that the motor is
placed in a speed ratio corresponding to the port receiving fluid from
the selected port conduit. The valve is spring biased to supp1y fluid
to the low speed ratio. A selectively actuated solenoid operatively
associated with the valve positions the valve to supply fluid to the
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high speed port to place the motor in the high speed ratio. However,
when fluid pressure reaches a predetermined level for the selected port
conduit a pressure sensor placed in the selected port conduit will send
an impulse to disable the solenoid, thus positioning or maintaining the
valve in a position for supplying fluid to the low speed port conduit
corresponding to the low speed port.
FIGURE 1 is a schematic diagram of the hydraulic and electrical
circuitry employed in the preferred embodiment of the present invention.
In FIG. 1, a fluid controlled two-speed ratio motor 14 of a con-
ventional hydrostatic motor-pump system is schematically illustrated.
The motor 14 could commonly be found in a winch for use on a crane.
Hydraulic fluid goes from a pump (not shown) through load conduit 16 to
motor 14 and then returns to the pump through return conduit 18.
Hydraulic fluid from a conduit 20, which branches from load conduit 16,
is supplied to low speed port 22 or high speed port 24 by selective
adjustment of directional control valve 26. Spring 28 urges directional
control valve 26 to a low speed port actuation position 27 shown in
FIG. 1 wherein conduit 20 supplies fluid through a low speed supply
section 25 of directional control valve 26 and low speed port conduit 30
to low speed port 22 to place the motor in a low speed rat~o. In the
low speed ratio, hydraulic fluid from the flu~d controls (not shown) in
motor 14 is returned to conduit 18 through h~gh speed port 24, high
speed port conduit 32, a low speed return section 31, and motor dis-
charge conduit 19.
To place the motor 14 in a high speed ratin, fluid control valve 26
is shifted rightward from the low speed actuation position 27 shown in
FIG. 1 to a high speed actuation position 29 to provide hydraulic fluid
from conduit 20 through high speed supply section 33 of valve 26 and
conduit 32 to high speed port 24. Hydraulic fluid returns via low speed
port 22, low speed port conduit 30, high speed return section 35 of
valve 26, and motor discharge conduit 19 to return conduit 18 for
recirculation through the pump.
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High speed switch 36 (which is preferably a push button) of an
electrical control circuit 34 shown in the upper portion of FIG. 1 is
manually closed to energize solenoid coil 38 to shift directional
control valve 26 from its FIG. 1 low speed ratio port actuatation
position 27 to the rightward high speed port actuation position 29.
Additionally, relay circuit coil 40 is also energized when switch 36 is
closed. Normally spaced-apart contacts 42 are closed by the energiza-
tion of relay circuit coil 40 for maintaining solenoid coil 38 in an
activated condition to retain the directional control valve 26 in the
high speed position 29 until either a low speed switch 37 is manually
depressed or the pressure in high speed port conduit 32 exceeds a
certain predetermined pressure level (4000 psi for the above-discussed
winch application).
Pressure sensor 44 which is preferably a spring biased piston (not
shown) is interposed in and responsive to fluid pressure in high speed
port conduit 32 and is fluid connected to a high speed pressure switch
46 of circuit 34 by high speed pilot conduit 45. High speed pressure
switch 46 is urged by spring 48 to a closed contact position. When the
motor 14 is in its high speed ratio and the pressure in conduit 32
exceeds the predetermined pressure level, high speed pressure switch 46
switches to an open positlon against the blas of a sprlng 48 and thus
de-energlzes solenold coll 38 and relay clrcu~t coll 40 to allow sprlng
28 to shift dlrectlonal control valve 26 back to lts FIG. 1 low speed
ratio position 27 and to open contacts 42. After high speed pressure
switch 46 has opened in response to an impulse from sensor 44, further
manual actuatlon of high speed switch 36 will not energize the circuit
since the pressure in conduit 32 will not decrease to deactivate sensor
44 until the load on the motor 14 which caused the increased pressure on
the conduit line is released.
In the preferred embodiment the hydraulic piston of sensor 44 in
line 32 which is normally spring biased to a closed position will shift
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under hydraulic pressure to compress the piston spring and increase the
hydraulic pressure in pilot line 45 to cause high speed pressure switch
46 to switch to an open position resisting the bias of spring 48 in
switch 46.
Pressure sensor 50 which is also preferably a spring biased piston
(not shown) is interposed in low speed port conduit 30 and responsive to
fluid pressure and sensor 50 is fluid connected to a low speed pressure
switch 52 of circuit 34 by low speed pilot conduit 54. Low speed
pressure switch 52 is urged by a spring 53 to a closed contact position.
When the motor 14 is in its low speed ratio and the pressure in conduit
30 exceeds a certain predetermined pressure level (preferably 1800 psi
in the above-discussed preferred embodiment), low speed pressure switch
52 switches to an open position to break circuit 34 and therefore
actuation of high speed contact switch 36 will not energize solenoid
coil 38 or relay circuit coil 40 to shift the directional control valve
to its high speed port actuation position 29.
In the preferred embodiment the hydraulic piston in line 30, which
is normally spring biased to a closed position, will shift under hydraulic
pressure to compress the piston spring (not shown) of sensor 50 and
increase the hydraulic pressure in pilot line 54 to cause low speed
pressure switch 52 to switch to an open position resisting the bias of
the spring 53 associated therewith. Once low speed pressure swftch 52
has opened, manual actuation of high speed switch 36 will not energlze
solenoid coil 38 to shift directional control valve 26 to its high speed
port actuation position 29 since the pressure in conduit 30 will not
decrease below a predetermined level to allow the hydraulic piston of
sensor SO to return to its normally closed position until the load on
the motor 14 which caused the increased pressure on the conduit line 30
is released.
It will be appreciated that numerous modifications may be made
without departing from the scope of this invention. For example, the
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hydraulic sensors 44 and 50, high speed and low speed pilot hydraulic
conduit lines 45 and 54 and pressure switches 46 and 52 respectively
could be replaced by a microprocessor and pressure transducer(s) if
desired. Additionally, the motor employed in this invention could be of
any power-driven type which utilized fluid controls to change from one
speed ratio to another. Although hydraulic fluid controls are disclosed
in the preferred embodiment, pneumatic or other types of fluid controls
could also be used. Moreover, although the preferred embodiment contem-
plated for the present invention is used on the motor of a winch con-
nected with a crane, the instant invention is not limited to the present
application but could be used whenever it is desirable to monitor and
control the fluid pressure of the fluid controls of a motor.
From the foregoing it is believed that those familiar with the art
will readily recognize and appreciate the novel concepts and features of
the present invention. Obviously, while the invention has been des-
cribed in relation to only a preferred embodiment, numerous variations,
changes, and substitutions of equivalents will present themselves to
persons skilled in the art and may be made without necessarily departing
from the scope of the principles of this invention. As a result, the
embodiment described herein is subject to various modlfications, changes,
and the like wlth the scope of thls lnventlon belng determlned solely by
reference to the claims appended hereto.
