Note: Descriptions are shown in the official language in which they were submitted.
-1- 2012-6&~$
TRAILER LIFTING AND LOWERING SYSTEM
Background and Summary
This invention relates to an air/hydraulic
system for raising and lowering a load, such as for use
on with a trailer or the like.
Various systems are known and used for
lifting and lowering of a load such as a trailer. In
most such systems, it is generally necessary for pres-
surized air to be supplied to the system whenever it is
desired to raise or lower the legs. Further, such
systems generally require a pair of oil reservoirs, one
of which supplies oil to a booster pump for extending
the legs, and the other of which provides oil under
pressure for retracting the legs by means of a manual
retraction pump or the like.
The present invention is designed to provide
a simplified system for raising and lowering legs for
use on a trailer or the like. In accordance with the
invention, a pressurized fluid operated lifting and
lowering system includes one or more fluid operated
extendible and retractable legs, with each leg
including biasing means urging the leg to retract.
Lock valve means is associated with each leg and is
movable between an open position and a closed
position. The lock valve means in its open position
allows fluid flow to or from the leg, and in its closed
position prevents fluid flow to or from the leg. The
lock valve means preferably includes a movable internal
member which selectively allows fluid flow there-
through. The lock valve means is normally urged to itsclosed position.
Selectively actuable extension means is
provided for moving the lock valve means to its open
position and selectively supplying pressurized fluid to
3S the leg to overcome the biasing means and to cause the
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leg to extend To extend the legs under load, preferably,
a booster pump is-manually actuated by means of a booster
valve which selectively supplies pressurized air to the
booster pump. The booster pump draws fluid from the
reservoir, and pumps intensified fluid pressure to the
legs to extend the legs. Operation of the booster pump
provides pressurized fluid to the lock valve, which
opens the lock valve and passes into the leg for
extending the leg. When pressurized fluid is not
supplied to the lock valve, the lock valve returns to
its closed position to prevent fluid flow there-
through.
Selectively actuable retraction means is
provided for moving the lock valve means to its open
position. The retraction means preferably includes
means for simultaneously cutting off the supply of
pressurized air to the system when the lock valve means
is moved to its open position. When this occurs, fluid
is allowed to be expelled from the leg due to
retraction of the leg by the action of the biasing
- means. In a preferred embodiment, the retraction means
is a pressurized fluid actuated system.
A master valve is preferably provided for
moving the lock valve to its open position when pressurized
fluid is not supplied thereto, for allowing fluid to be
expelled to retract the legs. The master valve is
preferably interconnected with an air valve so that
actuation of the master valve controls the supply of
pressurized air to the system. The master valve is
movable between an extend position and a retract --
position, with a neutral position midway between the
extend and retract positions. The master valve is
preferably interconnected with the fluid reservoir
mentioned above, and in its retract position supplies
fluid pressure to an external actuator which moves the
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201 2685
--3--
lock valve to its open position for allowing fluid to
flow therethrough to retract the legs. The master
valve includes a piston disposed within a passage, with
the passage being interconnected with the external lock
valve actuating means. A first opening provides com-
munication between the passage and the reservoir, and a
second opening provides communication between the
passage and the lock valve. A third opening provides
communication between the legs and the reservoir. When
in its retract position, the master valve piston covers
the first opening to cut off the supply of fluid
pressure thereto, while maintaining fluid pressure in
the line communicating the passage with the external
actuating means. In this position, the third opening
is exposed so as to allow fluid flow from the leg
through the lock valve and the third opening, and back
into the reservoir. As noted, the supply of
pressurized air to the reservoir is cut off and vented
so as to allow flow of fluid to the reservoir.
Brief Description of the Drawings
The drawings illustrate the best mode
presently contemplated of carrying out the invention.
In the drawings:
FIG. 1 is a schematic representation of a
prior art system for lifting and lowering of legs
adapted for mounting to a trailer;
FIG. 2 is a schematic representation of the
lifting and lowering system according to the invention;
FIG. 3 is a sectional view of a leg for use
in the system of FIG. 2, with a lock valve constructed
according to the invention mounted to its upper end;
FIG. 4 is a longitudinal sectional view of
the lock valve as shown in FIG. 3 mounted to the upper
end of a leg;
--- 20 1 2685
FIG. 5 is a sectional view of the master
valve for use in the system of FIG. 2;
FIG. 6 is a sectional view taken generally
along line 6-6 of FIG. 5, showing the master valve in
its extend position;
FIG. 7 is a view similar to FIG. 6, showing
the master valve in its retract position;
FIG. 8 is a view similar to FIG. 6, showing
the master valve in its neutral position; and
FIG. 9 is a sectional view of the booster
valve for use in the system of FIG. 2.
Detailed Description of the Prior Art
Referring to FIG. 1, a prior art system for
lifting and lowering of a pair of legs 10, 12, in the
form of hydraulically actuated cylinders, includes a
conduit 14 adapted for connection to a pressurized air
conduit 16, such as the emergency brake line of a
tractor/trailer combination. Legs 10, 12 are adapted
for connection to the underside of a trailer. An
isolator valve 18 is movable between an operating
position as shown, and a venting position. A master
valve 20 is connected with isolator valve 18 by means
of a conduit 22. Master valve 20 is a three position
valve in which the center position represents an "off"
position, the leftwardmost position an "extend"
position, and the rightwardmost position, as shown, a
"retract" position. A conduit 24 interconnects master
valve 20 with a retract side oil tank 26, and a conduit
28 interconnects master valve 20 with an extend side
oil tank 30. A reciprocable booster valve 32 is inter-
connected with master valve 20 by means of a conduit34, and a conduit 36 interconnects booster valve 32
with a booster pump 38. As is known, booster pump 38
includes a piston 40 and a stem 42. When master valve
20 is in its extend position, tank 30 is pressurized
- 201 2685
-5-
and tank 26 is vented. The pressurization of tank 30
causes fluid to flow through booster pump 38 to a
conduit 44 and a leveling valve 46, and through a pair
of conduits 48, 50 to a pair of lock valves 52, 54
associated with legs 10, 12, respectively to extend the
legs to ground. Thereafter, air pressure alone cannot
lift the load, and booster valve 32 is cycled so as to
selectively provide pressurized air to the air side of
piston 40, the end of stem 42 provides fluid pressure
through conduit 44 and leveling valve 46 to conduits
48, 50, and lock valves 52, 54, thereby causing further
extension of legs 10, 12. A manual retract pump 52 is
provided for retracting legs 10, 12. When master valve
20 is placed in its retract position, tank 30 is vented
and tank 26 is pressurized by air passing through
conduit 24. Pressurized fluid passes through a hand
pump 56 to simultaneously open lock valves 52, 54 and
supply pressurized fluid to retract legs 10, 12,
respectively. When master valve 20 is in its retract
position, an additional passage in master valve 20
connects conduit 24 to tank 30 to allow fluid to be
expelled from legs 10, 12. When air is absent from
conduit 16, hand pump 56 provides a means to retract
legs 10, 12 by drawing oil from tank 26 due to
generation of a partial vacuum, and generating pres-
surized fluid to simultaneously open lock valves 52, 54
and supply pressurized fluid to retract legs 10, 12.
Detailed Description of the Preferred Embodiment
Referring to FIG. 2, a pair of legs 60, 62
are adapted for connection to the underside of a
trailer or the like. Legs 60, 62 include upper
housings 64, 66, fixed upper portions 68, 70 extendible
and retractable lower portions 72, 74, and feet 76,
78. The details of construction of legs 60, 62 will be
described hereafter.
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As in the prior system, a glad hand 80 is
adapted for connection to a source of pressurized air,
such as the emergency brake line of a tractor or the
like. A conduit 81 interconnects glad hand 80 with a
check valve 81a, a conduit 82, and an air valve 84.
Air valve 84 includes a body 86 having ports 88, 90 and
92. Air valve body 86 further includes a hole 94 which
receives a slidably mounted retaining member 96. As
shown, a conduit 98 is provided between air conduit 81a
and a housing 100 within which retaining member 96 is
disposed, so that pressurized air is provided to the
head of retaining member 96 when pressurized air is
supplied to the system.
Air valve 84 includes a rotor 102 mounted to
a shaft 104. Passages 106, 108 open onto the outer
face of rotor 102. A depression 109 is provided on the
outer edge of rotor 102.
Conduit 82 is connected to air valve port 88,
and a conduit 110 is connected between air valve port
90 and a booster valve 112. Booster valve 112 is
constructed somewhat similarly to air valve 84,
including a body 114 having ports 116, 118, 120, and a
rotor 122. Rotor 122 is mounted to a rotatable shaft
124, and is provided with a passage 126.
A conduit 128 interconnects booster valve
port 118 with the air side of an air/hydraulic booster
pump 130 of conventional construction. The oil side of
booster pump 130 receives oil from a tank 132 through a
conduit 134. A double check valve 136 is disposed
between booster pump 130 and conduit 134. Check valve
136 provides one-way flow of oil from tank 132 to a
pumping chamber 138 associated with booster pump 130
during the suction stroke of the booster pump, and one-
way flow of oil from pumping chamber 138 to a conduit
140 during the pumping stroke.
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-- 20 1 2685
A tank 141 is piggybacked onto tank 132 and
is separated from tank 132 by means of a cap, shown at
141a.
A conduit 142 is provided between air conduit
110 and tank 132 for pressurizing oil within tank 132
when pressurized air is supplied to the system, and for
venting tank 132 when air valve 84 is put in its off or
retract position.
A conduit 144 interconnects conduit 140 with
10 upper housing 66 of leg 62. A conduit 146 intercon-
nects conduit 140 with upper housing 64 of leg 60
through a conduit 148.
A master valve, illustrated schematically at
150, includes a pair of side-by-side body portions 152,
15 154. Air valve 84 is interconnected with master valve
150 such that shaft 104 extends through master valve
body portions 152, 154 to provide simultaneous
operation of air valve 84 and master valve 150. This
commonality of valve shaft 104 with air valve 84 and
20 master valve body portions 152, 154 is illustrated by
dashed conduit 156.
A cam actuator 158 is connected to valve
shaft 104 at body portion 152, and is housed within a
cavity 160. Body portion 152 is provided with a
25 passage 162 in communication with cavity 160. A piston
164 is slidably mounted within passage 162, and a stem
166 is connected to piston 164 and bears against cam
actuator 158. A spring 170 biases piston 164 and stem
166 against cam actuator 158.
In a like manner, a cam actuator 172 is
mounted to valve shaft 104 at body portion 154, and is
housed within a cavity 174. Cavities 160, 174 are in
communication with each other. A passage 176 is
provided in body portion 154, within which is disposed
a piston 178. A stem 180 extends between piston 178
-8- 201 2685
and a cam actuator 172. A spring 184 biases piston 178
and stem 180 against cam actuator member 172.
Openings 186, 188 communicate between
passages 162, 176, respectively, and conduits 190, lg2,
respectively. Conduits 190, 192 unite in a conduit 194
which interconnects conduits 190, 192 with tank 132.
An opening 196 communicates between passage
176 in body portion 154 and a conduit 198, which
communicates with conduits 146, 148.
Passages 200, 202 are formed in body portions
152, 154, respectively and communicate between cavities
160, 174, respectively and conduits 204, 206,
respectively which unite in a conduit 208 to provide
communication with tank 132.
A conduit 210 extends between an opening 212
in body portion 152 and upper housing 64 associated
with leg 60. Likewise, a conduit 214 extends between
an opening 216 in body portion 154 and upper housing 66
associated with leg 62. Openings 212, 216 are in
communication with passages 162, 176, respectively in
body portions 152, 154.
A conduit 216a connects tank 132 with a check
valve 216b, which allows pressurized fluid to flow from
tank 132, conduit 216a and check valve 216b to a
conduit 216c and to enter tank 141. Check valve 216b
allows pressurized fluid to fill tank 141 when tank 132
is pressurized. Conduit 216c connects tank 141 to a
check valve 216d, which is connected by conduit 216a to
tank 132. Check valve 216d has an opening bias which
results in pressure being maintained in tank 141 at all
times.
With reference to FIG. 3, leg 60 is
illustrated in detail. It is understood that legs 60,
62 are identical in construction, so that the descrip-
tion of leg 60 applies equally to leg 62.
- 201 2685
_9_
As shown, upper housing portion 64 is mounted
to the upper end of fixed upper portion 68, which is in
the form of a substantially cylindrical tube.
Extendible and retractable lower portion 72 is also in
the form of a substantially cylindrical tube, having a
smaller diameter than that of upper portion 68. Upper
portion 68 and lower portion 72 are substantially
coaxial. Lower portion 72 is mounted for slidable
movement relative to upper portion 68, and spacers and
seals are provided in the gap between upper portion 68
and lower portion 72.
Lower portion 72 has a cap 217 fixed at its
lower end, to which a soft shoe assembly 218 is
connected, of which foot 76 is a part. The construc-
tion of shoe assembly 218 is known in the art. Arubber boot 220 extends between the lower end of lower
portion 72 and the lower end of fixed upper portion 68,
acting to prevent contamination of the seals disposed
between upper portion 68 and lower portion 72.
Lower portion 72 includes an internal cavity
222. A pair of coaxial coil springs are mounted within
cavity 222. The inner coil spring is illustrated at
224, and the outer coil spring is illustrated 226.
Springs 224, 226 are mounted at their lower ends to
inner and outer end members 228, 230, respectively,
which are connected together by welding or the like.
Inner end member 228 includes an internally threaded
passage for receiving a bolt 232, which extends upward-
ly from cap 217 to fix springs 224, 226 relative to the
lower end of lower portion 72. In a similar fashion,
springs 224, 226 are fixed at their upper ends to upper
inner and outer end members 234, 236, which are
connected together such as by welding or the like.
Upper inner end member 234 includes an internally
threaded passage for receiving a bolt 238, which is
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--10--
adjustable to provide a selected amount of pretension
in springs 224, 226. As shown, bolt 238 extends
through upper housing 64 so that its head portion,
shown at 240, is disposed adjacent the upper surface of
5 upper housing 64.
With continued reference to FIG. 3, a lock
valve assembly, shown generally at 242, is mounted
within a substantially horizontal passage, shown at
244, provided within upper housing 64. An upper
passage 246 is provided in housing 64 for communication
between passage 244 and the outer surface of housing
64, and a lower passage 248 is formed in housing 64 to
provide communication between passage 244 and cavity
222 of lower leg portion 72.
Reference is now made to FIG. 4 which
illustrates the internal construction of lock valve
242. As shown, lock valve 242 includes a body portion
250 having an internal cavity 252. A plug 254 and an
O-ring 256 are mounted to the leftward end of body 250
for sealing cavity 252. An angled seat 258 is provided
at the rightward end of cavity 252, which terminates in
a passage 260. Ports 262, 264 provide communication
between lock valve cavity 252 and housing cavity 244 at
housing lower passage 248. Similarly, ports 266, 268
provide communication between lock valve passage 260
and housing cavity 244 at housing upper passage 246.
An internal plunger assembly is mounted
within lock valve cavity 252 and passage 260. The
plunger assembly includes a stem 270 to which a pair of
end retaining rings 272, 274 are mounted. As shown,
stem 270 extends through passage 260 and an end wall
276 of lock valve body portion 250. A coil spring 278
is disposed between the rightward surface of end wall
276 and the leftward surface of right retaining ring
274 so as to bias stem 270 rightwardly to its closed
20 1 2685
position as shown in FIG. 4. In this position, an O-
ring 280 is sandwiched between the rightward surface of
end retaining ring 272 and angled seat 258 of cavity
252, so as to normally seal cavity 252 from passage
260.
An actuating cup-shaped piston 282 is
slidably mounted within a cylinder formed by a side
wall 284 extending from lock valve end wall 276. A
spring 286 is disposed between the rightward surface of
side wall 276 and piston 282 for urging piston 282
rightwardly out of contact with the rightward end of
plunger stem 270. Housing 64 includes a passage 288
which is selectively provided with hydraulic fluid
pressure, as will be explained, to selectively move
piston 282 leftwardly against the force of spring 286
to contact plunger stem 270. When this occurs, such
leftward movement of piston 282 causes leftward move-
ment of plunger ring 272 to unseat from seat 258 to
move lock valve 242 to its open position, thus
providing communication between lock valve passage 260
and lock valve cavity 252.
A bleeder system is preferably interconnected
with passage 288 to purge air from conduits 190, 192,
194, 214, 210, 188, 176, 216, 186, 162, 212 and 288.
Operation of the system will be described
with reference to FIGS. 2, 3 and 4. When it is desired
to extend legs 60, 62, master valve stem 104 is rotated
until its extend position as shown in FIG. 2 is
attained. In this position, pressurized air is
supplied to booster valve 112 and to oil tank 132.
Lower portions 72, 74 of legs 60, 62 will extend until
feet 76, 78 contact the ground, due to the air pressure
supplied to oil within tank 132. When feet 76, 78
contact the ground, the resistance in conduit 140 is
greater than the air pressure supplied to oil in tank
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12 ~ 201 2685
132, so that the upper check valve in check valve
assembly 136 remains closed. When this occurs,
continued extension of legs 60, 62 is achieved by
reciprocating booster valve 112 between an operative
5 position and an inoperative position (shown in FIG.
2). In its operative position, booster valve 112 is
positioned 90 clockwise from its position shown in
FIG. 2, so that passage 126 provides communication
between booster valve ports 116, 118 to provide air
pressure through conduit 128 to the head of the booster
valve piston, causing a power stroke of the piston.
This forces oil from pumping chamber 138 through the
upper check valve in check valve assembly 136 and into
conduits 144, 146 for supply through appropriate
fittings to the upper passages (such as 246, FIG. 3) in
upper housings 64, 66 provided on legs 60, 62. Such
pressurized fluid communicates through ports 266, 268
(FIG. 4) to passage 260, and then overcomes the biasing
force provided by spring 278 to move the lock valve
plunger assembly to its open position. When this
occurs, such pressurized fluid passes into lock valve
cavity 252 and through lock valve ports 262, 264 to
housing cavity 244, then passing through lower housing
passage 248 and into cavity 222 of leg lower portion 72
(FIG. 3) to extend leg 60. The same action occurs with
respect to leg 62. When the booster pump power stroke
is completed, the lock valve plunger returns to its
closed position by the action of spring 278 so as to
maintain the legs as extended. Booster valve 112 is
then moved to its inoperative, or venting, position as
shown in FIG. 2, wherein air supplied to the head of
the booster pump piston is vented to atmosphere. When
this occurs, pressurized fluid from tank 132 passes
through conduit 134 and the lower check valve in check
valve assembly 136 so as to fill pumping chamber 138.
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-13- 201 2685
Booster valve 112 is then again moved to its operative
position to provide another power stroke of the booster
pump piston. This action is repeated until the desired
amount of extension of legs 60, 62 is attained.
During extension of legs 60, 62, master valve
pistons 164, 178 remain in the position as shown in
FIG. 2 so that opening 196 is blocked, thereby prevent-
ing communication between opening 196 and cavity 174.
After desired extension of legs 60, 62, valve
shaft 104 is returned to its neutral position, which is
45 counterclockwise from the position shown in FIG.
2. In this position, air valve 84 is positioned so
that the supply of pressurized air to the system is cut
off, and venting to atmosphere occurs through air valve
port 90, passage 108, and port 92. Cam actuators 158,
172 assume a neutral position, in which opening 196
remains blocked and openings 186, 188 remain open.
When it is desired to retract legs 60, 62,
master valve shaft 104 is moved 45 counterclockwise
from the neutral position so that air valve passage 106
provides communication between air valve ports 90 and
92, thus venting any pressurized air supplied to the
system to atmosphere. Pressurized air may still be
applied to the system through glad hand 80, thus
forcing retaining member 96 downwardly so as to engage
depression 109 formed in rotor 102. This acts to
maintain rotor 102, and thereby valve shaft 104, in the
retract position, 90 counterclockwise from the
position shown in FIG. 2 so long as air is supplied to
glad hand 80.
When valve shaft 104 is rotated to the
retract position as described above, cam actuator
members 158, 172 force master valve pistons 164, 178
leftwardly within passages 162, 176, respectively.
When this occurs, opening 196 in master valve body
201 2685
-14-
portion 154 is unblocked so as to provide communication
between conduit 198 and master valve cavity 174. At
the same time, openings 186, 188, which supply
pressurized fluid to passages 162, 176 are blocked by
the heads of pistons 164, 178. Leftward movement of
pistons 164, 178 within passages 162, 176 provides
pressurized fluid in conduits 210, 214, which is
communicated to upper housings 64, 66 of legs 60, 62,
respectively. Referring now to FIGS. 3 and 4, such
supply of pressurized hydraulic fluid to upper housings
64, 66 is communicated through passages, such as 288
(FIG. 4) to the rightward side of the actuating
pistons, such as 282, associated with the lock valves,
such as 242. As described previously, this action
causes the lock valve plunger to move to its open
position, thus providing communication between lock
valve cavity 252 and lock valve passage 260. When this
occurs, the force of springs 224, 226 and/or load
causes lower leg portion 72 to retract within upper leg
portion 68, expelling fluid from cavity 222 through
lower passage 248, lock valve assembly 242 and upper
passage 246. Fluid expelled from leg 62 flows through
conduits 144 and 146, and fluid expelled from leg 60
flows through conduit 148. The expelled fluid within
conduits 146, 148 then flows through conduit 198 and
opening 196 in master valve body portion 154 and into
master valve cavities 174, 160. Such fluid then
continues to flow through openings 200, 202 and
conduits 204, 206 to conduit 208, and thereafter to
tank 132.
It should be appreciated that leg retraction
can occur whether or not pressurized air is supplied to
the system, due to the presence of the springs within
legs 60, 62 which urge the legs to retract. When pres-
surized air is supplied to the system, however, valve
-15- 20 1 2685
shaft 104 is retained in its retract position by the
action of retaining member 96 engaging depression 109
in air valve rotor 102. When pressurized air is not
supplied to the system through glad hand 80, valve
shaft 104 must be manually held in its retract position
until legs 60, 62 are fully retracted. If this is not
done, a torsion spring associated with valve shaft 104
will return shaft 104 to its neutral position, thus
preventing further leg retraction.
With reference to FIGS. 5-8, a physical
embodiment of master valve 150, with air valve 84
attached, is illustrated. Where possible, like
reference characters from FIG. 2 will be used to
facilitate clarity. With reference to FIG. 5, the
torsion spring which returns master valve shaft 104 to
its neutral position is shown at 292. The remainder of
FIG. 5 is believed to be self-explanatory when viewed
in connection with FIG. 2.
FIG. 6 shows master valve 150 with shaft 104
in its extend position. FIG. 7 illustrates master
valve 150 with shaft 104 moved to its retract position
in which cam 172 forces piston 178 to its leftwardmost
position. In this position, passage 188 is blocked and
passage 196 unblocked so as to provide communication
with cavity 174. FIG. 8 illustrates master valve 150
in its neutral position.
FIG. 9 illustrates a physical embodiment of
booster valve 112, and is believed to be self-
explanatory with reference to FIG. 2.
Various alternatives and modifications are
contemplated as being within the scope of the following
claims particularly pointing out and distinctly
claiming the subject matter regarded as the invention.
