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Sept. 17, 1946.‘
‘H. F. VICKERS -
I
2,407,694
HOIST CONTROD AND DRIVE
Filed Aug. 5.1940
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SéPt- 17, 1946-
H. F. VICKERS
-
' 2,407,694.
HOIST GONTROL AND DRIVE
Filed Aug. 5, 1940
2 Sheets-‘Sheet 2
5%
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_ ATTORNEYS.
Patented Sept. 17, 1946
2,407,694
UNITED STATES PATEl‘lT OFFICE
2,407,694
HQIST CONTROL AND DRIVE
Harry F. Vickers, Detroit, Mich, assignor to Vick- ‘
ers Incorporated, Detroit, Mich., a corporation
of‘ Michigan
Application August a, 1940, Serial No. 350,519
19 Claims.
This invention relates to a hoist control and
has particularly to do with a hoist mechanism
driven by a hydraulic motor and a hydraulic
pump.
It is an object of the present invention to pro
vide a control mechanism which is normally
servo-operated but which may be operated with
out servo power in case of failure of certain ele
ments of the system.
A further object is to provide a servo con
trolled unit in which the speed signal is limited
by the position of, the hoist. Another object of
the invention has to do with a provision for
safely stopping the elevator or hoist in case of
(on. 18-7-28)
2
motor 24 be operating. Consequently, the energy
of the electric circuit is taken from the motor.
One line 32 leads from the motor to the solenoid
33'. Another line 33 leads to a switch 34 which
is connected to a door 35, shown diagrammati
cally at the upper station A. From switch 34,
which is closed when door 35 is closed, the circuit
to solenoid 3|] follows a line 36 to a starting switch
31. A line 38 connects through a switch 39 to
line 40 leading to solenoid 33. Switch 39 is oper
atively connected to a door-4| at the lower sta
tion B.
'
l
‘
At each station, A and B, is provided a limit
switch 42 and 43, respectively. When car In is
power failure.
15 at its lower limit, as shown in the drawings, switch
Another object of the invention has to do with
43 is open. When the car reaches its upper posi
a means for maintaining the hydraulic pressure
tion, switch 42 is open. During the travel of the
source at slight output when the motor is inoper
car between the stations the starting switch 3'!
ative and means ‘for bypassing said output.
may be released since both switches 42 and 43
Other objects and features of the invention 20 will be closed and the circuit between. lines 36
having to do with details of construction and
and 38 is completed by a line 44, switch 42, a line
the hydraulic circuit, including the operation of
45 and switch 43. Line 33 is shunted to line 35
the same, will be brought out in the following
through a line 46 and a switch 41 which is closed
description and claims.
when the car I0 is at its upper station by a cam
In the drawings:
25 slide Illa on the car. This shunting of line 46
Fig. 1 is a circuit diagram ‘substantially dia
grammatic showing the various elements of the
system.
of
Fig. 2 is an enlarged sectional view of a portion
1 showing the main elements of the hy- 1
draulic control.
In Fig. 1 ,a hoist car ii) is supported by an oper
ating cable || controlled by a drum l2. The
drum I2 is driven by a reversible, variable speed,
motor I3 through suitable gears l4 and I5. A
brake unit It‘ is connected to gear I5 by a gear
|'|. Connected also to the drum l2 through suit
able gearing IB is a cam wheel I9. Housed within
permits operation of the car In between two load
ing levels at the upper station with door 35 open.
The switch 42 controls the upper level and a
switch 48 in line 45 controls the lower level, the
switch 48 having an arm 49 which operates the
switch when pressed downwardly but not when
pressed upwardly. A small projection 50 on the
car is arranged to contact switch 49. Switches
42 and 43 are operated by a projection 5| on the
car.
Pump 2| is connected to motor |3 by conduits
55 and 56. The pump 2| has a movable member
5'! which, when shifted to the right as viewed in
Fig. 2, will cause pressure to be directed from
hydraulic pump 2| and a control valve block 22 40 conduit 56 to conduit 55 and thence to the motor
(see Fig. 2). The pump 2| is driven by a shaft
to effect a hoisting movement. When the mov
23 from an electric motor 24 which also drives
able member 51 is displaced to the left, there will
a pilot or booster pump 25. Tank 25 serves as a
be a lowering action. Since the weight of the
main source of liquid for the hydraulic control
elevator will tend to drive the motor IS, the line
circuit and a supplemental tank 23 has functions
55 will be under pressure and ?uid will be flowing
which will he described later.
through pump 2| to line 56. There is a closed
An electrical circuit is provided to permit oper
circuit between pump 2| and motor I3 and this
ation of the elevator 0r hoist only when certain
circuit is super-charged through a check valve
conditions are met. A solenoid 33 operates a
53 open to a line 59 and booster pump 25. In
venting valve 3| in the valve block 22. The vent 50 the event of failure of the booster pump, replen
ing valve which will be described later is of such
ishing of line 56 may take place through a con
a nature that the elevator cannot ‘be operated
duit 6B and a gravity valve 6| supplied by a tank
unless it is shifted against a spring 3| (1 by the
‘26 which is located at a level sunicient to supply
energized solenoid 3D. The ?rst condition for
a head of oil.
the movement of the hoist is that the electric 55
The basic control of‘ the hoist is through the
a tank 28 are a reversible variable displacement
2,407,694
3
4
shown, the conduit 88 is connected through a
conduit 9| to the venting valve and through the
venting valve to a conduit 92 leading to conduit
56 of the main pump. Consequently, there is no
pressure in either cylinders 89 or 8| and the
springs 85 and 86 are free to act. These springs
are so adjusted that they will hold the movable
rod 65 has a restriction 6'! which servesas a
head 51 slightly off center toward the hoist side.
valve, as will be described later. The piston 63
The output of the pump 2| is, therefore, through
is to be shifted by pressure from the booster
pump 25, said pressure being conducted to the‘ 10 conduit 55 but this output is bypassed through
conduit 88, the valve restriction 6'|, conduit 9|,
housing 22 by a line 68. When venting valve 3|
venting valve 3| and conduit 92.
is in the position shown in Fig. 2, the solenoid
The effect of shifting of the venting valve 3|
30 being deenergized, line 68- is vented to a line
to the right is to connect cylinder 89 to the
69 leading to tank 26. Above the venting valve
3| in housing 22 is a servo-valve l9 and above 15 pressure in conduit 55/ through conduit 69,
around piston rod 65, through a conduit 93, to
the servo-valve is a shuttle valve '||. . .As shown
conduit 89. Branch 88a also connects cylinder
in the drawings, the shuttle valve normally by
9| to the pressure in conduit 55. Line 81 is neces
passes conduits 12 and 13 leading to the. respec—
sary to insure shifting of piston 83 by equal dis
tive ends of cylinder 64. 'When venting valve 3|
is shifted to the left, as viewed in the drawings, 20 placement from either line of the closed operative
movable member 51 on pump 2|; this member is
pivoted as at 62 and normally is shifted by a servo
mechanism which controls the movement of a
motor piston 63. The piston 63 is located in a
cylinder 64 and has a rod 65 connected to a link
66 and by the link to the movable head 51. The
by the energization of the solenoid 30, line 68
will be cut off from, line 69 and pressure from
booster pump 25 will be directed to a line 14.
Pressure in line 14 will shift shuttle valve ‘H to
the right, closing conduit 12 from conduit 13,
but opening the end of conduit 14 to conduit 13,
thus admitting pressure to the differential end of
pressure piston 63. Because of the location of
circuit. \
In addition to the brake |6, another safety de
vice is provided in a safety latch 95 which is con
trolled by a spring pressed piston 96. A piston
91 Within a cylinder 98 at brake I6 and also the
piston 96 are controlled by pressure from/ the
booster pump 25 by reason of lines 99 and I09
leading, respectively, from conduit 68. When
tank 26, and the connection pipe 69, there is a , . venting valve 3| is open, the brake |6 will be en
head of oil maintained on lines ‘l2, 13 when the 30 gaged and the latch 95 will be engaged providing
the car is in its uppermost position. Upon the
valves are in the position shown and the hoist is
shifting of valve 3| .and the building up of pres
not‘being operated. Consequently, when valve
sure in line 68, piston 96 will beretracted and,
10 is in the position shown, a shifting of valve
similarly, piston 9‘l‘will be retracted, thus releas
‘H to admitpressure to the differential end of
piston 63, will not cause shifting of the ‘piston 35 ing latch 95 and brake l6.
In case of failure of the booster pump or any
since the liquid to the left of piston63 cannot
of the pressure lines connected therewith, a
escape. The servo-valve 10 is controlled by a rod
mechanism is provided to permit operation of the
15 leading from a shaft 16 controlled by a
hoist without servo-power. A shaft |0|, operable
lever 11.
Assuming that the elevator is to be hoisted, 4O by a lever I92, controls, by suitable arm connec
tions, the piston 96 and the piston 91. For ex
lever "is lifted and by this movement rod 15 .
ample, if lever I92 is shifted from its P position
is raised. Since piston 63 is temporarily sta
to its W position, latch 95 will be retracted and
brake l6 will be released. A further connection
valve 10 to the left, through va lever 18a and link‘
18b. This will open conduit 12 to tank conduit 45 is provided, through a rod ‘I03, So that upon such
shifting of lever I92, the valve 16 will be locked
69 and permit piston 63 to be shifted to the left
tionary. a movement of a bell crank 18 will shift
by pressure in conduit 13. This will cause a shift
in its neutral position as viewed in Fig. 2. The
it to the right.
tion at lever 11 now controls the pump head 51
locking of valve 19 is accomplished by a cam I94
ing of the movable head 51 to a hoisting position.
which is moved by the shifting of rod I33. Since,
‘A restriction ‘I9 in conduit 12 limits the velocity
of the piston 63 and, therefore, limits accelera 50 due to booster pump failure, pressure is absent
from lines 68 and 14, the valve ‘H is spring im
tion or'deceleration of the hoist. If the hoist is
pelled to bypass the stroke cylinder lines 12 and
to be lowered, lever 11 is lowered, thus resulting
13
to the replenishing tank line 69. Stroke pis
in a downward‘movement of rod 15. This will
ton 63 is, therefore, allowed free movement and
shift the valve 10 to the right by reason of the
movement of bell crank 18 and lever ‘18a. Pres 55 the differential bypass is compensated for by the
connection with tank 26. ,The head of oil from
sure will then be admitted from line 68 to line
the tank -26 prevents aeration. Manual applica
12 and the head end of piston 63, thereby shifting
In each case, of course, a move
without lost motion through rod 15, bell crank 18
ment of the piston 63 and its rod 65, will com
pensate for movement of the valve “land there 60 and lever 18a, which is now pivoted at link 18b.
Replenishing of the operating circuit is obtained
will thus be a follow-up or servo movement.
through gravity check 6| from tank 26. The re
At each side of pump 2| are cylinders 80 and
-mainder of the circuit functions the same as
8| in which are located pistons 82 and 83; these
previously described.
.
pistons have rods extending to a projection 84 on
The tank 26 is fed by surplus oil from the
the movable head 51 and each is urged toward 65
booster pump through line I05 and check valve
this projection by springs 85 and 86. A conduit
I06. The over?ow from this tank is carried
81 connects one end of the cylinder of piston 83
through line I61 to tank 20. The booster pump
to conduit 56 while the other end is connected
normally draws oil through oil ?lters I08 in tank
by a conduit 88 to conduit 55 and also to housing ‘
22 at the restriction in the rod 65. The cylinder 70 26 and a conduit I89. These two ?lters are
:mounted parallel in the circuit and are provided ‘
'80 for piston 82 is connected by a conduit 89 to
with plunger operated check valves. By this
the right end of venting valve 3|. When the
means one of them may be removed at a time
venting valve is in the position shown, the con
while the other is operating. Air line H9 trans
diiit 89 is connected to a conduit 90 leading to
the tank conduit 69. Similarly, with the parts as 75 fers air between tanks 29 and '26 due to ?uid dis
5
2,407,694
placement. When the booster pump 25 is vented
through valve 3|, a restriction HI maintains a
back pressure in line 59 thus keeping the operat
ing circuit supercharged even while idling.
Cam l9 limits the amount the lever 11 may be
shifted. As the lever shaft 16 is also connected,
as previous'y described, to a servo-valve ‘it which
controls pump offset, it can be seen that cam l9
controls the maximum rate of speed as well as
deceleration and acceleration of the hoist. This 10
is accomplished by reason of a lever or follower
H2 which rides on the circumference of the cam
which is properly shaped to control the movement
of the shaft in conjunction with the movement of
the motor l3 and the hoist car It]. A cam H3 on
car IE is arranged to contact a lever its on its
movement from the top level at the upper station
6
means onsaid pump shiftable to "hoist” or
“lower” positions for controlling the direction
and volume of flow, and means'acting on said
shiftable means to maintain it slightly toward‘a
hoist position when the motor is not being op
erated.
2. In a hoisting mechanism and control, an
elevating mechanism, a hydraulic motor for driv
ingsaid mechanism, and apumping ‘circuit for
furnishing liquid under pressure to drive said
motor including a variable displacement pump,
means on said pump shiftable' to “hoist” or
“lower” positions for controlling the direction
and volume of flow, control means acting on said
shiftable means to maintain it slightly toward a
hoist position when the motor-is not being op
erated, and valve means for bypassing the slight
to the lower level to cause deceleration as the
hoist is moved between levels at the upper sta
“hoist” output of said pump when said motor is
any of the lines. In case of power failure, that
is, failure of the electric power driving motor 25,
means has been provided to stop the hoist in the
means on said pump shiftable ‘to “hoist” or
not being operated.
tion. This is accomplished through a rod H5 20
3. In a hoisting mechanism. and control, an
which connects to the shaft 13.
elevating mechanism, a hydraulic motor for driv
An object of the present invention has been to
ing said mechanism, and a pumping circuit for
provide a, hoist circuit which will perform safely
furnishing liquid under pressure to drive said
even in the event of power failure or rupture of
motor including'a variable displacement pump,
“lo-wer”.positions for controlling the direction
and volume of ?ow, control means acting on said
shiftable means to maintain it slightly toward a
hoist position when the motor is not being op
smoothest and safest possible manner. While in
the lowering stroke, it will be noted that line 38
remains open to line 9| through the restriction 30 erated. valve means for bypassing the slight
6? in rod 65 of stroke piston 63. In the event of
“hoist” output of said pump when said motor is
power failure while lowering, the solenoid 3i}
not being operated, and additional means respon
would be deenergized and the spring Sic. will shift
sive to a predetermined operating signal for re
the valve 3! to a venting position. The result will
moving the effect of said control means and
be a centering of the pump yoke 5‘! by the spring
cutting off said bypass.
pressed plunger or piston 82 and at the same time,
4. In a hoisting mechanism and control, an
the operating circuit is bypassed through lines
elevating mechanism, a hydraulic reversible mo
88, 9!, 92, a check valve H1, and a restriction
tor for driving said mechanism, and a pumping
H8. A sufficient resistance is thus affected in
circuit for furnishing liquid under pressure to
this bypassing to aid the‘brake H5 in gradually
drive said motor including a variable displace
bringing the load to a safe stop. The brake, of
ment pump, means on said pump shift-able to
course, will be automatically engaged upon a
“hoist” or “lower” positions for controlling the
shifting of valve 3% to venting position. In the
direction and volume of ?ow, control means act
case of power failure while hoisting, line 83 is
ing on said. shiftable means to maintain it slightly
closed by rod 65 since piston 53 is shifted to the 45 toward a “hoist” position when the motor is not
left and hence the pump 2! will continue to raise
being operated comprising spring pressed plung
the hoist carried on 'by the inertia by the high
ers located in cylinders, valve means for bypass
speed electric motor. Brake IE will, of course, be
ing the slight “hoist” output of said pump when
engaged as before but a free wheeling device
said motor is not being operated, and additional
shown diagrammatically at H9, permits overrun
means responsive to a, predetermined operating
while hoisting. The load is thus gradually de
celerated by reason of gravity and this prevents
the cable from whipping. As soon as the load
comes to stop, the brake l5 will function to hold
it and also the pressure will drop in line 55 thus
permitting the plunger 83 to center the pump
yoke. It will be seen that the pump yoke is al
ways centered as a result of power failure and,
as a. consequence, the electric motor is lightly
loaded upon resumption of power.
t will further be seen that in the event of the
rupture of any of the pressure lines, the brake
IE will be engaged. In the event of the rupture
of line 56, the booster pump pressure would be
vented through line 59 and check valve 58 thus
causing an engagement of brake l6. Rupture of
line 55 would also vent the booster pump pressure
through check valve I20, again causing the en
gagement of brake l 6.
Iclaim:
1. In a hoisting mechanism and control, an
signal for cutting off said bypass and directing
said pump output to said spring pressed plungers
to remove the effect thereof on said shiftable
means.
5. In a hoisting mechanism and control, an
elevating mechanism, a hydraulic reversible mo
tor for driving said mechanism, and a pumping
circuit for furnishing liquid under pressure to
drive said motor including a variable displace
ment pump, shiftable means on said pump mov
able to “hoist” or “lower” positions for control
ling the direction and volume of flow, spring
pressed plungers acting on said shiftable means
to maintain the same slightly toward a hoist po
sition when the motor is not being operated, an
independent source of pilot pressure, a pressure
operated means responsive to said pilot pres
sure and to a predetermined operating signal to
control the position of said shiftable means dur
ing operation of said motor, and a valve means
arranged to bypass the slight “hoist” output of
elevating mechanism, a hydraulic motor for driv
said pump and to bypass the pilot pressure when
ing said mechanism, and a pumping circuit for
the motor is not being operated, and shiftable to
furnishing liquid under pressure to drive said
direct said pilot pressure to said pressure op~
motor including a variable displacement pump, 75 erated means and to direct said pump output. to
2,407,694
7
said plungers to remove the effect thereof on said
shiftable means.
'
‘ 6. In a hoisting mechanism and control, an
elevating mechanism, a hydraulic motor for driv
ing said mechanism, a control cam driven by said
motor, a pumping circuit for furnishing liquid
8
a motor, a variable displacement pump for fur
nishing liquid under pressure to said motor, mov
able means on said pump for controlling the di
rection and volume of ?ow, a follow-up mecha
nism for actuating said movable member com
prising a hydraulic motor, a valve for controlling
pilot pressure thereto, and means connecting the
same to effect follow-up movement, manual
means for controlling said valve, brake means
trolling the direction and volume of ?ow by its 10 for locking said motor except when released by
pilot pressure, and means for locking certain ele
relative displacement from a neutral position, an
ments of said follow-up mechanism and for re
operating lever, means operably connecting said
leasing said brake means to permit direct manual
lever and shiftable means whereby shifting of
operation in case of failure of pilot pressure.‘
said lever will veffect displacement of said shift
under pressure to drive said motor including a
variable displacement pump, means on said pump
shiftable to “hoist” or “lower” positions for con
12. In a hoist driving system, a, hydraulic mo
able means, and means connecting said lever and 15
tor, a-pump for furnishing pressure- thereto, a
said cam whereby the limits of movement of said
closed circuit connecting said pump and said mo
lever and said shiftable means are directly con
tor, a pilot pump for furnishing replacement liq
trolled by the position of said cam in its move
uid to said closed circuit, a liquid supply tank
ment withthe motor, said cam being shaped to
control acceleration and deceleration of said 20 mounted'at a level above said circuit, and a
‘valve connecting said tank with said circuit
motor.
whereby said tank may furnish replacement liq
'7. In a hoisting mechanism and control, an
elevating mechanism, a hydraulic motor for driv
ing said mechanism, a variable delivery reversible
pump for furnishing liquid under pressure to said
uid to said closed circuit in event of failure of said pilot pump.
,
13. In a hoisting system, a hoisting element,
motor, a movable member on said pump to con
trol the output thereof, a source of pilot pressure,
power means for actuating the same between a.
means and said safety latch whereby said pilot
means whereby said element may be shifted be
lower station and an upper station, gate means at
each of said stations to prevent access to the
a follow-up valve for utilizing said pilot pressure
path of movement of said element while it is
to‘shift said movable member, a'brake means for
said motor and a safety latch for said elevating 30 between said stations, a control system opera
tively connecting said gate means with said power
mechanism, means connected with said brake
pressure functions at the instance of an op
erator to release the same, and an independent
tween said upper and lower stations only when
said gate means are properly closed, and means
mechanism operable upon failure of said pilot
pressure to unlock said safety latch, release said
brake,-'and render said follow-up valve inoper
able.
between two- de?ned and spaced levels at the
upper station when said upper gate is open.
14. In a, hoisting system, a hoisting element,
8. In a hoisting mechanism and control, a hy
draulic motor for driving a hoist mechanism, a
reversible variable delivery pump for furnishing
liquid under pressure to drive said motor, a mov
able member on said pump for controlling, by
7 its displacement, the direction and volume of
flow from said pump to said motor, a source of
power for driving said pump, and means respon
sive to a failure of said source of power for by
passing said pump during a lowering movement
of said hoist.
for permitting limited movement of said element
power means for actuating the same between a
lower station and an upper station, gate means
at each of said stations to prevent access to the
path of movement of said element while it is
between said stations, a control system opera
tively connecting said gate means with said
power means whereby said element may be shift
ed only when said gate means are properly closed,
means for permitting limited movement of said
element between two levels at the top station '
when said top gate is open, and means for au
tomatically decelerating said element at the lower
' 9. In a hoisting mechanism and control, a hy 50
end of its movement between levels at the upper
draulic motor for driving a hoist mechanism, a
station.
'
reversible variable delivery pump for furnishing
liquid under pressure to drive said motor, a mov
able member on said pump for controlling, by its
15. In a hoisting mechanism and control, a
said pump during a lowering movement of said
said motor and pump, a pressure release-brake
hydraulic driving motor, an elevating mechanism
to
be driven by said motor, a pumping circuit
displacement, the direction and volume of flow 55
including a variable delivery pump for furnishing
from said pump to said motor, a source of power
liquid under pressure to drive said motor, lines
for driving said-pump, means responsive to a
connecting the respective inlets and outlets of
failure of said source of power for bypassing
hoist, and means for restricting said bypass flow 60 operably connected to said mechanism for brak
ing against downward movement only of said
to cause gradual deceleration of said hoist.
hoist, control means for bypassing said pump
10. In a hoist, a driving mechanism comprising
motor lines, control means for controlling pres
a motor. a variable displacement pump for fur
sure to said brake, electric power means for con
nishing liquid under pressure to said motor, mov
65 trolling said control means, and means respon
sive to power failure during hoisting to operate
rection and volume of flow, a follow-up mech
said control means to effect engagement of said
anism for actuating said movable member, com
brake to hold said hoist as it comes to rest, and
prising a hydraulic motor, a valve for controlling
responsive to power vfailure during lowering to
pilot pressure thereto and means connecting the
same to effect follow-up movement, manual 70 open said bypass and effect engagement of said
brake to bring said mechanism to rest.
means for controlling said valve, and means for
16. In a hoisting mechanism and control, a
locking certain elements of said follow-up mech
hydraulic driving motor, an elevating mechanism
anism to permit direct manual operation in case
to be driven by said motor, a pumping circuit
of failure of pilot pressure.
~ 1 11. In a hoist, a driving mechanism comprising 75 including a variable delivery pump for furnish
able means on said pump for controlling the di
2,407,694
ing liquid under pressure to drive said motor,
lines connecting the respective inlets and outlets
of said motor and pump, a pressure release-brake
operably connected to said mechanism for brak
ing against downward movement only of said
hoist, control means for bypassing said pump
motor lines, control means for controlling pres
sure to said brake, electric power means for con
trolling said control means, means responsive to
power failure during hoisting to operate said
control means to effect engagement of said brake
to hold said hoist as it comes to rest, and respon
sive to power failure during lowering to open said
bypass and eifect engagement of said brake to
bring said mechanism to rest, and means forming
a restriction in said bypass to aid in slowing
down said motor during power failure in lower
mg.
17. In a hoisting mechanism and control, an
elevating mechanism, a hydraulic motor for driv
ing said mechanism, and a pumping circuit for
furnishing liquid under pressure to drive said
motor including a variable displacement pump,
means on said pump shiftable to “hoist" or
“lower” positions for controlling the direction
and volume of flow, means acting on said shift
able means to move the same to substantially
said brake to bring said mechanism to rest, said
shiftable means being returned to substantially
neutral position by the means acting thereon in
each case of power failure.
18. In a hydraulic mechanism and control, an
operating mechanism, a hydraulic motor element
for driving said mechanism, a pumping circuit
for furnishing liquid under pressure to drive said
motor element including a pump element, means
on one of said elements shiftable to positions for
controlling the direction and volume of flow by
its relative displacement from a neutral position,
an operating lever, means operably connecting
said lever and shiftable means whereby shifting
of said lever will effect displacement of said shift
able means, and means operably connecting said
lever and said operating mechanism to limit the
movement of said lever and said shiftable means
in a varying degree dependent on the position
of the operating mechanism in its movement with
the motor.
:
19. In a hydraulic mechanism and control, an
operating mechanism, a hydraulic motor element
for driving said mechanism, a; pumping circuit
for furnishing liquid under pressure to drive said
motor element including a pump element, means
on one of said elements shiftable to positions for
neutral position in the absence of operating pres.
controlling
the direction and volume of flow by
sure in said pumping circuit but rendered inoper
its
relative
displacement
from a neutral position,
able by operating pressure, a pressure release 30 an operating lever, means
operably connecting
brake operably connected to said mechanism for
said lever and shiftable means whereby shifting
braking against downward movement only of
of said lever will effect displacement of said
said hoist, control means for bypassing said
shiftable means, a cam operated by said motor,
pumping circuit, control means for controlling
and means connecting said lever and said cam
pressure to said brake, electric power means for 35 comprising a cam follower mounted on said lever
controlling said control means, and means re
adapted to follow said cam‘ and to limit the
sponsive to power failure during hoisting to oper__
movement of said lever in varying degrees de
ate said control means to eifect engagement of
pendent on the movement of the motor from its
said brake to hold said hoist as it comes to rest,
starting position.
‘
and responsive to power failure during lowering 40
to open said bypass and effect engagement of
HARRY F. VICKERS.
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