Note: Descriptions are shown in the official language in which they were submitted.
99~3~
Background of the Invention
This invention relates to an actuator for the landing
gear assembly of the trailer of a tractor-trailer combination.
Conventionally, such a trailer includes a pair of laterally spaced
landing gear feet which extend downwardly from the front portion
of the trailer and contact the ground to support the trailer in an
elevated position when the trailer is detached from the tractor.
When the trailer is attached to the tractor, the landing gear feet
are retracted upwardly to prevent the feet froIn engaging the grs~und
10 while the trailer is being towed by the tractor.
In most trailers, the landing gear feet are connected
by a laterally extending cross-shaft which extends the feet when
rotated in one direction and retracts the feet when rotated in the
opposite direction. The cross-shaft usually is connected to a two-
speed gear box located outboard of one of the feet and may be selectively
turned at either a high speed or a low speed by a manually operated
hand crank attached to the input shaft of the gear box.
It has been recognized that considerable time and
effort is required to manually operate the hand crank. Accordingly,
20 power-operated actuators have been provided to rotate the cross-shaft
in either direction in order to extend or retract the landing gear feet.
One such power-operated landing gear actuator is disclosed in
Vandenberg United States Patent 4,116, 315 and employs a reciprocating
pneumatic act-uator which is operated by the same source of
pressurized air that is used to operate the brakes of the tractor-
trailer combination. Another pneurnatically operated landing gear actuator
has been so]d by Northwest Manufacturing Corporation of Camanche,
Iowa under the trademark GEAR MAT~. That actuator includes two-
speed gearing which allows the cross-shaft to be rotated selectively
30 at a high or low speed
438
Summary of the [nvention
_ _ .
The general aim of the present invention is to provide
a new and improved landing gear actuator which, when compared with
prior actuators, may be installed more quickly and easily on &e trailer
and which, at the same time, is of more compact, lightweight, reliable
and eeonomical construction.
A more detailed object is to provide a landing gear
actuator which is capable of being easily mounted on the trailer without
need of first removing and then replacing one of the landing gear feet.
Another object of the invention is to provide a landing
gear aetuator whieh is capable of rotating the cross-shaft at either high
or low speeds without need of incorporating two-speed gearing into the
aetuator itself.
A further object is to achieve the foregoing by uniquely
conneeting the landing gear aetuator direetly to the existing erankshaft
of the trailer and by utilizing the existing gear box of the trailer to
enable the aetuator to rotate the eross-shaft at either high or low speeds.
Still further objeets of the invention are to provide a
highly reliable and effective eyele valve for effeeting automatie and
20 eyelie reversal of the reeiproeating pneumatie aetuator, to provide a
reliable manually operable eontrol valve for switehing the aetuator on
and off, and to provide a eontrol valve whieh automatieally switehes
the aetuator off when the landing gear feet reaeh their fully retraeted
positions .
Yet another object of the invention is to provide a
landing gear actuator in whieh the reciproeating motion of the pneumati
aetuator is eonverted to rotary motion by uniquely arranged ratchets,
pawls and gears of relatively compact and simple eonstruction.
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~5~31~
The invention also resides in the p:rovision of novel
means for .-activclting and inactivating the pawls to enable the
reciprocating pneumatic actuator to selectively rotate the cross-
shaft in eittler directioll.
In br ief, the invention resides in an actuator for a
semi-trailer landing gear assembly having a pair of laterally spaced
extendible and retractable feet, said landing gear assembly further
including a gear mechanism located adjacent one oE said feet and
having gearing, said gear mechanism having an input defined by a
10 crankshaft and having an output defined by a cross-shaft extending
between said feet, said crankshaft being spaced radially from. said
cross-shaft and being connected to said cross-shaft by said gearing,
there being a fixed angular relationship between the axis of said
crankshaft and the axis of said cross-shaft, said cross-shaft being
operable to extend or retract the feet in dependence upon the direction
of rotation of said crankshaft, said actuator comprising a housing,
means for mounting said housing at a location disposed adjacent to
and outboard of said one foot, a rotatable member carried by said
housing and rotatable about an axis coinciding with the axis of the
20 crankshaft, means for connecting said rotatable member to an end
portion of said crankshaft, power-operated means carried by said
housing and having a reciprocating element for rotating said member,
and means for selectively causing said reciprocating element to rotate
said member in either a clockwise or a counterclockwise direction,
said member acting through said crankshaft and said gearing to rotate
said cross-shaft.
These and other objects and advantages of the invention
will become more apparent from the following detailed description
when taken in conjunction with the accornpanying drawings.
-2A -
~L~.lS5~38
Bricf Description of the l)ra~,vings
. .
FIC;URE 1 is a fragmentary perspective view of a
typical trailer equipped wi~ a new and improved landing gear actuator
incorporating the unique features of the present invention.
FIG. 2 is an enlarged fragmentary cross-section
taken substantially along the line 2-2 of FIG. 1.
FIG. 3 is a cross-section taken substantially along
the line 3-3 of FIG. 2 and shows the actuator set to retract the landing
gear feet.
FIG. 4 is a fragmentary view of parts illustrated in
FIG. 3 and shows certain parts of the actuator in moved positions
during retraction of the feet.
FIG. 5 is a view similar to FIG. 3 but shows the
actuator set to extend the landing gear feet.
FIG. 6 is a fragmentary view of parts illustrated in
FIG. 5 and shows certain parts of the actuator in moved positions
as the feet are extended.
FIGS. 7 and 8 are enlarged fragmentary cross-sections
taken substantially along the lines 7-7 and 8-8, respectively, of FIG. 5.
FIG. 9 is a schematic view of the cycle valve, the
control valve and the pneumatic actuator and shows the pneumatic
flow circuit associated therewith.
Detailed Description of the Preferred Embodiment
As shown in the drawings for purposes of illustration,
the invention is embodied in an actuator 10 for extending and retracting
the landing gear of the trailer 11 of a tractor-trailer combination
~i.e., a semi). The landing gear forms part of the trailer itself
and includes a pair of laterally spaced pads or feet 1~. The latter
are pivotally mounted on the lower ends of vertical legs 14 which are
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S~3~
slideably received within upright sleeves 15 attached by mounting
brackets 16 to the forward encl portion oE the ~railer. The feet and
the legs ar e retracted upwardly when the trailer is coupled to the
tractor so as to prevent the feet from contacting the ground during
towing of the trailer. When the trailer is to be uncoupled from the
tractor, the feet and legs are extended downwardly to jack the trailer
upwardly off of the "fifth wheel" of the tractor and to ena~le the
trailer to stand alone.
A rotatable member in the form of a cross-shaft 17
10 extends laterally between the sleeves lS near the upper end of the
legs 14 and is effective to extend the legs when rotated in one direction
and to retract the legs when rotated in the opposite direction.
Various types of mechanisms may coact with the shaft to cause the
legs to extend or retract when the shaft is rotated. In this particular
instance, a nut 18 (FIG. 2)is attached rigidly to the upper end portion
of each leg and is threaded onto a lead screw 19 which is rotatably
journaled within the sleeve 15. Meshing bevel gears 20 are attached
to the shaft 17 and to the upper end of the screw 19 and turn the
screw in one direction or the other in dependence upon the direction
20 of rotation of the shaft. As the screws are turned, the nuts either
advance downwardly or upwardly so as to extend or retract the legs.
Conventionally, the cross-shaft 17 forms the output
of a gear box 21 which is attached to the outboard side of one of the
sleeves 15. The input of the gear box is formed by an outwardly
extending crankshaft 22(FIG. 2) whose inner end portion in this instance
is formed by a sleeve 23. The latter carries large and small pinions
24 and 25 and is slideably mounted on a shaft 26 within the gear box
21. When the crankshaft 22 is pulled outwardly, ~e large pinion 24
meshes with a small pinion 27 on the cross-shaEt 17 as shown in FIG.
38
2 so Lhat, ~Ihen the crankshaft is turned at a given speed, the cross-
shaft is rot~ted at a faster speed but with a relatively low torque input.
This is the hi~h gear setting of the gear box 21 and usually is used
to effect rapid retraction of the legs 14 when the trailer 11 is being
lowered and the power requirernents are low. When the legs are to
be extended to lift the trailer, the crankshaft 22 is pushed inwardly
to cause the sleeve 23 to slide inwardly on the shaft 26 and to bring
the small pinion 25 on the sleeve into meshing engagement with a
large pinion 28 on the cross-sha~t 17. Upon rotation of the crankshaft
with the gear box in its low gear setting, the cross-shaft is rotated
at comparatively low speed but with a relatively high input torque
to develop the power necessary to extend the legs and lift the trailer.
In many trailers, a hand crank (not shown) is attached
to the outer end of the crankshaft 22 and may be manually turned to
rotate the cross-shaft 17 and extend and retract the legs 14. To
avoid the time and effort required to manually operate the crank,
some trailers are equipped with power-operated actuators which are
capable of rotating the cross-shaft in one direction or the other to
effect automatic extension and retraction of the legs.
In one of its aspects, the present invention contemplates
the provision of a new and improved power-operated landing gear
actuator 10 which is characterized by the fact that the actuator is
attached to and acts directly on the crankshaft 22 rather than being
connected to the cross-shaft 17 at some point along that shaft. ~s a
result, the actuator rnay be installed in a readily accessible location
outboard of one of the legs 14 and may be quickly installed on the
trailer 11 without need of removing the leg 14 and the sleeve 15 in
order to gain access to the cross-shaft 17. Moreover, the actuator
10 utilizes the existing gear box 21 to effect a shirt between high and
--5--
~1 lS~4~3
low gears and thus the actuator itself need not be encumbered with
a separate two-speed transmis6ion.
More specifically, the act-uator 10 includes a housing 30
preferably located outboard of the gear box 21 and adapted to be attached
rigidly to the acljacent sleeve 15 by a mounting bracket 31 (FIG. 1).
in carrying out the invention, the outer end portion of the crankshaft 22
extends laterally through the side walls of the housing 30 and terminates
outwardly of the outer side wall. A sleeve 32 (FIG. 2) is telescoped
over the outer end portion of the crankshaft and is connected rigidly
thereto by a pin 33 which extends radially through the sleeve and the
crankshaft. A bushing 34 is secured tightly within the sleeve 32 and
is adapted to rotate therewith. The bushing receives a coupling device
34a with rotatable clearance, the coupling device being partially
surrounded by a flexible protective boot 35. Pivotally and slideably
connected at 36 to the outer end portion of the coupling device 34 is a
shift lever 37 which is pivotally connected near its mid-point to the
outer side wall of the housing 30 as indicated at 38. When the shift
lever is swung counterclockwise from the position shown in FIG. 2, it
acts through the coupling device 34a, the bushing 34, the sleeve 32 and
the pin 33 to push the crankshaft 22 inwardly and set the gear box 21 in
low gear. Reverse swinging of the lever sets the gear box in high gear
as shown in FIG. 2. Because of the bushing 34, rotation of the crankshaft
22 is not transmitted to the coupling device 34a and the lever 37.
Further in keeping with the invention, a power-rotated
member 40 (FIGS. 2 and 3) acts through the pin 33 to rotate the
crankshaft 22 in either of two directions with the crankshaft acting
through the gear box 21 and the cross-shaft 17 to extend or retract the
legs 14. Herein, the member 40 is in the form of a tubular hub disposed
within the housing 30 and rotatably journaled in sleeve bearings 41
43~
which are suppor ted by the .side walls of the housing. The hub 40 is
telescoped over the cr ankshaft 22 and the sleeve 32 and is formed with
two diametrically spaced slots or keyways 42 which slideably receive
the protruding ends of the pin 33 . ~s a r esult of the pin and the keyways,
rotation of the hub 40 is transmitted to the crankshaft 22 and yet, at the
same time, the crankshaft is capable of sliding axially relative to the
hub when the lever 37 is pivoted to shift the gear box 21 between high
gear and low gear.
To rotate the hub 40, and in keeping with the invention, a
gear 44 (FIGS. 2 and 3) is secured to the hub and preferably is formed
integrally with the hub as shown in FIG. 2. A one-way ratchet wheel 45
(FIG. 3) is located alongside the gear and is formed integrally with the
gear and the hub. Located within the housing 30 is a second gear 46 (FIG.
3) which meshes with the gear 44. A one-way ratchet wheel 47 is formed
integrally with one side of the gear 46 and both are formed integrally with
a hub 48 which is rotatably journaled in sleeve bearings 49 ~FIG. 1)
supported by the side walls of the housing 30. The ratchets 45 and 47 are
disposed in a common plane and the teeth of each face in the same direction.
Coacting with the ratchets 45 and 47 are pawls 50 and 51
(FIG. 3), respectively, each having one edge formed with multiple
teeth. Each pawl is mounted on a reciprocating ~Irive member 52 to
move substantially tangentially of its respective ratchet. In addition,
each pawl is pivotally mounted on the drive member by a pivoted pin
53 and is adapted to swing upwardly and downwardly between active
and inactive positions with respect to its ratchet. When each pawl is
swung upwardly to its active position, its teeth contact the teeth of
the associated ratchet (see, for example, the pawl 51 in FIG. 4).
The teeth of each pawl are released from and are spaced downwardly
from the teeth of the ratchet when the pawl is swung downwardly to
its inactive position as indicated, for example, by the pawl 50 in
--7--
31~
FIG. 4. Cantilevere(l leaf springs 5~ ~re located beneath the pawls
and have free ends which bear against the undersides of the pawls
near the free ends thereof to urge the pawls upwardly to their active
positions. ~he opposite end oE each spring is anchored to the upper
surface of the bottom of the drive member 52. Herein, the drive
member is in the ~orm of a U-shaped channel whose bottom is
supported by rollers 55 which span the side walls of the housing 30.
The pawls are located between the side walls of the channel-shaped
drive member 52.
Meang are provided for selectively shifting each of
the pawls 50 and 51 between its active and inactive positions with
one pawl being shifted to its active position when the other pawl is
shi~ted to its inactive position. Herein, these means comprise a
lever 60 (FIGS. 1 and 3) which is secured to a hori~ontal pin 61
(FIGS. 3 and 7), the latter being rotatably supported by the outer
side wall of the housing 30. The outer end portion of the pin projects
outwardly through the outer side wall and is connected rigidly to an
elongated handle 62 which forms part of the lever. As shown in
FIG. 3, the lever 60 also includes two oppositely extending arms
63 and 64 which overlie rollers 65 and 66 secured to and extending
outwardly from the pawls 50 and 51, respectively. When the handle
62 is turned in a counterclockwise position to the position shown in
FIG. 3, the arm 63 engages the roller 65 on the pawl 50 and cams
that pawl downwardly to its inactive position, the roller being recei~ed
within a notch 67 in the outer side of the drive member 5~. At the
same time, the arm 64 swings upwardly away from the roller 66 on
the pawl 51 so as to enable the latter pawl to pivot upwardly to its
active position under the urging of the underlying spring 54. Clockwise
swinging of the handle to the position shown in FIG. 5 results in the
38
arm 64 pressing the pawl 51 downwarclly to its inactive position and
in the arm 63 allowing the pawl 50 to spring upwardly to its active
position. If the handle 62 is centered between the positions shown
in FIGS. 3 and 5, the arms hold bc~th pawls 50 and 51 in a neutral
position in which neil;her pawl engages its associated ratchet 45 or
47. The handle is adapted to be held releasably in each of its positions
by a latch which herein is formed by a pair of leaf springs 70 (FTC~.
8). I~e springs are secured at 71 to the outer side wall of the
housing 30 and their laterally spaced lower end portions straddle
10 the arm 63. The frictional engagement between the ~springs 70 and
the arm 63 provides a retarding force which holds the handle 62 in
the position to which it is swung.
To reciprocate the drive member 52, a pneumatic
actuator 73 is operably connected to one end of the drive member.
In this instance, the pneumatic actuator comprises a cylinder 74
(FIGS. 1, 3 and 9) located outside of the housing 30 and secured to
the forward end thereof. Slideably received within the cylinder is a
rod 75 having one end projecting rearwardly from the cylinder and
attached to the forward end of the drive member. The other end of
20 the rod is attached to a piston 76 disposed within the cylinder and
located alongside a flexible diaphragm 77 which divides the cylinder
into front and rear chambers. When pressurized air is admitted
into the forward chamber, the piston 76, the rod 75 and the dri~Te
member 52 are advanced rearwardly. As air is exhausted from the
forward chamber, a coil spring 7~ retracts the piston, &e rod and
the drive member in a forward direction.
When the legs 14 are to be retracted, the shift lever
37 usually is swung counterclockwise to the position shown in FIG. 2
to set the gear box 21 in its high gear-high speed position. Also,
3'~
the handle 62 i~i swung counterclockwise to the position shown in
FIG. 3 to place the pawl 51 in its active positiorl and the pawl 50 in
its inactive position. Pressurized air then is alternately admitted
into and exhausted from the forward chamber of the cylinder 74 to
advance the drive mernber 52 rearwardly and to retract the drive
member forwardly. As the drive member is advanced, the teeth of
the pawl 51 engage the teeth of the ratchet 47 to turn the ratchet 47
and the gear 46 in a clockwise direction ~FIG. 4). The gear 46 rotates
the gear 44 and the crankshaft 22 in a counterclockwise direction to
effect retraction of the legs 14 at a relatively rapid rate. As the drive
member 52 advances, the inactive pawl 50 simply moves idly past the
ratchet 45 so as to leave the gear 44 free to be driven by the gear 46.
When the drive member is retracted, the pawl 51 moves o-ut of driving
engagement with the ratchet 47 and thus both gears momentarily remain
stationary until the drive member is again advanced to cause the pawl
51 to drive the ratchet 47 and the gear 46.
To extend the legs 14, the handle 62 is swung clockwise
to the position shown in FIG. 5 to place the pawl 51 in its inactive
position and to place the pawl 50 in its active position. In most
instances, the lever 37 usually will be left in the high gear position
as the legs are initially extended so that such extension can be effected
at a rapid rate.
As pressurized air is admitted into the cylinder 74 to
advance the drive member 52, the pawl 50 engages and drives the
ratchet 45 to rotate the gear 44 in a clockwise direction (see FIG. 6).
Accordingly, the crankshaft 22 is turned in a clockwise direction to
extend the legs 14. The inactive pawl 51 moves idly past the ratchet
47 during the advance stroke of the drive member 52, and the gear 46
simply rotates idly. When the drive member is retracted, the pawl 50
-10-
shifts out of driving engagement with the ratchet 45 so that both gears
are momentarily stationary.
Once the feet 12 contact the ground, the lever 37 may be
swung counter clockwise to set the gear box 21 in its low gear-high
~orque position. Accordingly, with continued actuation of the drive
member 52, the high torque necessary to lift the trailer 11 is applied
to the cross-shaft 17.
If there is no air supply available to actuate the cylinder
74, the actuator 10 may be manually operated. This is achieved by
10 placing the reversing handle 62 in the desired position, by placing the
hand crank with an adaptor thereon (not shown) in the hub 48 and by
turning the crank manually in the appropriate direction.
From the foregoing, it will be apparent that the present
invention brings to the art a new and improved landing gear actuator
10 which may be installed on the trailer 11 without need of removing
one of the legs 14 and sleeves 15 to gain access to the cross-shaft
17. Since the actuator acts through the crankshaft 22 and the gear
box 21, the actuator 10 need not be equipped with a two-speed
transmission. Accordingly, the actuator is easy to install and may
20 be of relatively compact, lightweight and economical construction.
In accordance with another aspect of the invention,
the actuator 10 is provided with a highly reliable and effective cycle
valve 80 (FIG. 9) for automatically effecting the alternate admission
and exhausting of pressurized air from the cylinder 74. Moreover,
the cycle valve is controlled by a highly reliable on-off valve 81
which is particularly characterized by its ability to automatically
shut off the actuator 10 once the legs 14 have been raised to their
fully retracted position.
38
~ \s shown in ~ G. 9, the c:ycle valve 80 includes a
body 82 which is mounted within the housing 30 on the bottom wall
thereof. Slideably Inounted within a bore 83 in the body and sealed
to the bore by an O-ring 84 is a spool 85 having a forwardly projecting
stem 86 of reduced cliameter disposed wi~ radial clearance in a
passage 87 ~,vhich constitutes a continuation OI the bore. An inlet
passage 88 for supply air (e.g., air at a pressure of about 100 p.s.i.)
is formed in the body 82 and leads into the passage 87 while an outlet
passage 90 leads out of the body and communicates with the forward
chamber of the cylinder 74 via a line 91. An exhaust passage 92
also is formed in one end of the body 82 and is open to atmosphere.
The passages 87, 90, and 92 are all adapted to communicate with a
chamber 93 located adjacent the forward end of the body.
Disposed within the chamber 93 and secured to the
stem 86 is an elastomeric valve member 94 having rear and forward
faces 95 and 96 whose diameters are larger than the diameters of
the passages 87 and 92, respectively. VVhen the valve member 94
is shifted to the right (FIG. 9), the valve face 96 closes off the exhaust
passage 92 while the valve face 95 opens up the passage 87 and
20 establishes communication between the supply passage 88 and the
cylinder 74 via the chamber 93, the passage 90 and the line 91.
Shifting of the valve member 94 to the left results in the valve face
95 closing the passage 87 to cut off the flow of supply air to the
cylinder 74 and, at the same time, the valve face 96 opens the passage
, 92 so that the air in the cylinder may exhaust to atmosphere by
way of the line 91, the passage 90, the chamber 93 and the passage 92.
Joined to and extending rearwardly from the spool
85 is a rod 98 (FIGS. 3 and 9) whose rear end portion is slideably
supported by an ear 99 which is turned upwardly from the bottom
-12-
~ ~159~38
wall of the housing 30. ~n L-shaped ~-~lemenl or bracket 100 (FIGS.
7 and 9) of inverted U-shaped cross-section is secured rigidly to
the lower side of the clrive member 52, the lower end portion of
the bracket lO0 being bifurcated and straddling thé rod as shown in
FIG. 7. The lower end portion of thè bracket is sandwiched between
two washers 101 and 102 (FIG. 9) which are telescoped slideably
over the rod 98. A coil spring 103 is telescoped over the rod and i9
located between the washer 102 and a third washer 104 which is
telescoped slideably over the rod and which abuts the rear end of
the spool 85. Another coil spring 105 is telescoped over the rod
adjacent the washer 101 and is adapted to enter into a counterbore
106 formed in a block 107 which is attached rigidly to the rear end
portion of the rod.
Let it be assumed that the piston 76 of the actuator 73
is fully retracted as shown in FIG. 9 and that pressurized supply air
is being delivered to the cycle valve 80 by way of the passage 88.
When the piston is fully retracted, the drive member 52 is in a
retracted position causing the bracket 100 to act through the washer
102, the spring 103 and the washer 104 to hold the spool 85 in an
20 open position shown in FIG. 9. With the spool th-us positioned, the
valve face 96 closes the exhaust passage 92 while the valve face 95
opens the passage 87. Accordingly, pressurized air is supplied to
the forward chamber of the cylinder 74 by way of the passages 88
and 87, the chamber 93, the passage 90 and the line 91, The piston
76 thus is shifted rearwardly to advance the drive member 52.
As the drive member 52 advances, the bracket 100
and the washer 101 slide rearwardly along the rod 98 and away from
the spring 103 and thus the mechanical force for holding the spool
85 in its open position is removed. The spool remains in that position,
-13-
;'~lS~38
however, by virtue of the pressurized air in the chamber 93 acting
against the valve face 95 and exerting a rightwardly directed force
on the spool. Accordingly, the piston 76 and the drive member 52
continue to advance rearwarclly.
~ s the drive member 52 approaches the énd of its advance
stroke, the spring 105 enters the counterbore 106 in the block 107 and
engages the bottom of the counterbore before the washer 101 engages
the block. With continued advancement of the drive member, the
spring 105 becomes compressed between the washer 101 and the bottom
of the counterbore 106. The washer 101 then engages the block 107
and thus the block is forced rearwardly and acts through the rod 98 to
shift the spool 85 to the left against the force exerted on the valve face
95 by the pressure in the chamber 93. Accordingly, the valve face 95
moves toward the passage 87 to cut off the flow of supply air to the
cylinder 74 and, at the same time, the valve face 96 moves away from
and opens the exhaust passage 92. As a result, air is e~austed from
the cylinder via the line 91, the passage 90, the chamber 93 and the
passage 92 to stop further rearward movement of the drive member 52.
When the valve face 96 first opens the exhaust passage 92, the compressed
spring 105 acts between the washer 101 and the block 107 to shift the
spool 85 rapidly to the left through its full stroke and thereby insure
full opening of the exhaust passage 92 and full closing of the supply
passage 87. The spring 78 thus starts retracting the piston 76 and
the drive member 52 in a forward direction.
Upon initial retraction of the drive member 52, the
bracket 100 starts sliding forwardly along the rod 98. The washer 101
and the spring 105 follow behind the bracket since, as shown in FIG. 1,
the housing 30 and the cycle valve 80 disposed therein are inclined
downwardly and forwardly and thus gravity causes the virasher 101 and
-14-
~ 5~3-~3~3
the spring 105 to move forwardly along the rod 98. As the bracket 100
moves away from the block 107, the mechanical force for holding the
spool ~5 in its closed position is removed from the rod 98. The spool,
however, is held in its closed position by the air pressure in the passage
87. That pressure acts against a land surface 108 formed at the junction
of the spool 85 and the stem 86. The area of the land 108 is larger than
the effective area of the valve face 95 when that face is sealed against
the passage 87. Accordingly, the force developed by the pressure acting
on the land 108 to urge the spool 85 to the left is greater than the opposing
force developed by the pressure acting on the valve face 9S and thus the
spool remains closed as the drive member 52 retracts.
When the drive member 52 approaches the end of its
retract stroke, the bracket 100 pushes the washer 102 against the spring
103 which, in turn, compresses against the washer 104 to avoid the
imposition of an abrupt shock load. After compressing, the spring 103
tends to act as a rigid link and thus the mechanical force applied to the
spool 85 by way of the spring overcomes the pressure acting against
the land 108 so that the spool rapidly shifts to the right to its open
position (FIG. 9) in order to open the passage 87 and close the passage
92 and thereby initiate another cycle. When the passage 87 is open,
the effective area of the valve face 95 is greater than the area of the
land 108 and thus the pressure in the chamber 93 tends to force the
spool 85 to the right to its open position.
Thus, the cycle valve 80 automatically admits pressurized
air into and exhausts pressurized air from the cylinder 74 in timed
relation with the movement of the drive memher 52 by virtue of the
valve being actuated by the drive member as the latter reaches the end
OI each stroke. The stroke of the drive member is significantly longer
than the stroke of the valve spool 85 but the air acting on the surfaces
95 and 108 is utilized to keep the cycle valve 80 either open or closed
-15-
~ rj~
<luring travel of the drive member between the ends of its stroke. As
a result of the springs 103 and 105, valve shifting is assured and no
abrupt shock loads are irnposed upon the valve 80 or on the housing 30
when the drive member 52 stops and reverses directions. The cycle
valve thus performs in a highly reliable and non-erratic manner and is
capable of experiencing a long service life.
As mentioned above, the on-off valve 81 controls the
supply of pressurized air to the cycle valve 80 and, in keeping with the
invention, shuts off the actuator 73 automatically once the legs 14 are
10 fully retracted. As shown in FIG. 9, the on-off valve 81 includes a
body 110 which is mounted beneath the bottom wall of the housing 30 at
right angles to the body 82 of the cycle valve 80. An o-utlet passage 111
is formed in the body 110 and communicates with the inlet passage 88 of
the cycle valve 80 to supply pressurized air to the cycle valver the
passage 111 also communicating with a chamber 112 in the body 110.
Also formed in the body 110 is a supply passage 113 which communicates
with the chamber 112 by means of an axial passage 114 in the body. The
supply passage 113 is connected to a line llS which in turn is connected
to a source of pressurized air (e.g., the same source which is used to
20 pressurize the brake system of the trailer 11).
A spool 116 (FIG. 9) is slideably mounted within a
bore 117 in the body 110 and is sealed therein by an O-ring 118.
Formed on one end of the spool 116 is a reduced-diameter stem ll9
which is received with radial clearance in the passage 114. The
stem carries a valve member 1~0 having valve faces 121 and 122,
the valve face 121 being adapted to close the passage 114 to seal that
passage from the chamber 112 and the passage 111. The valve face
122 is adapted to seat against the end of a housing 123 and to ciose
off passages 124 formed in the housing and communicating with a
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~ l S~ L~L38
ch~Lmber 125 therein, the chamber 125 being vented to atmosphere
by means of an exhaust passage 126 formed through the housing.
The housing 123 is attached to the inner end of the valve body 110.
~ttached to the oute~ end of the spool 116 is a knob
130 (FIG. 9) which may be pushed inwardly to open the valve 81 and
pulled outwardly to close the valve. A flexible boot 131 is connected
between the valve body 110 and the outer end of the spool 116 to
prevent dirt and the like from entering the bore 117.
When the knob 130 is manually pushed inwardly, the
10 Yalve member 120 is shifted to the left (FIG. 9) to cause the valve
face 121 to open the passage 114 and to cause the valve face 122 to
close the passages 124. As a result, supply air from the iine 115
flows to the cycle valve 80 via the passages 113 and 114, the chamber
112 and the passage 111 to effect operation of the actuator 73. By
virtue of the passages 124 being closed by the valve face 122, supply
air is prevented from escaping through the exhaust passage 126.
When the actuator 73 is to be turned off, the knob 130
is pulled outwardly (i. e., to the right in FIG. 9~ to shift the valve
member 120 and cause the valve face 122 to open the passages 124
20 and, at the same time, to cause the valve face 121 to close the
passage 119. ~s a result of the passage 114 being closed, the flow
of supply air to the cycle valve 80 is cut off. Although the pressure
of the supply air in the passage 114 acts against the valve face 121
and tends to shift the valve member 120 to the left, that same pressure
also acts against a land 135 located at the junction of the spool 116
and the stem 119. The effective area of the land 135 is greater
than the effective area of the valve face 121 when the latter is closed
and thus the supply air keeps the valve 81 closed. The open passages
124 vent the chamber ~ 12 through the exhaust passage 126 and thus
30 the chamber is free of any pressure tending to open the valve.
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3~
To effect automatic closing of the valve 81 when the
legs 14 are fully retracted, a plunger 136 (E~'~G. 9) is disposed within
the chamber 125 and its outer end is adapted to momentarily engage
the valve face 122 and shift the valve rnember 120 outwardly (or to
the right in FrG. 9) to close the valve 81. Formed on the inner end
of the plunger 136 is a head 137 which normally seats against and
closes a passage 138 in the inner end of the housing 123. The area
of the head 137 is significantly greater than the area of the passage 138.
A coil spring 139 is telescoped over the plunger 136 and is compressed
between the housing 123 and the head 137 to urge the latter to the left
into a closed position relative to the passage 138. The passage 138
communicates with the forward chamber of the cylinder 74 by means
of a line 140 which extends between the housing 123 and the cylinder.
When the legs 14 are to be retracted upwardly, the
driver of the truck need merely push the knob 130 inwardly to shift
the valve member 120 so that the valve face 121 opens the passage 114
and the valve face 122 engages the end of the housing 123 (see FIG. 9)~
As pressurized air flows to the cylinder 74 to retract the legs 14, the
pressure in the passage 114 holds the valve member 120 in the position
20 shown in FIG. 9 since the pressure ac~s against the relatively large
area of the open valve face 121. Accordingly, the driver need not
continue to push the knob 130 inwardly to hold the valve 81 open and
thus the driver r~ay leave the side of the trailer 11.
Once the legs 14 have been fully retracted, the pressure
, in the cylinder 74 builds to a value (e.g., 35 p.s.i.) which exceeds the
pressure (e.g., 20 p.s.i.) required to advance the drive member 52
when the legs are being retracted. The increased pressure in the
cylinder 74 is transmitted to the passage 138 via the line 140 and acts
against the head 137 to shift the plunger 136 outwardly or to the right.
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3~
Once the head opens the passage 138, the pressure in the passage acts
~gainst the full area of the head to snap the plunger 136 to the right with
a sharp rapid motion. 'Ihe right end of the plunger strikes the valve
face 122 and forces the valve member 120 to the right to close the
valve 81 to cut o~f the flow of pres6urized air to the cylinder 74 and
to thereby automatically turn off the actuator 73. When the prefisure
in the cylinder 74 and the line 140 is relieved, the spring 139 forces
the plunger 136 back to the position shown in FIG. 9 to close the
passage 140. It should be noted that there is no seal between the head
137 and the charnber 125 and thus air in the chamber is free to escape
to atmosphere through the vent passage 126 when the spring 139 returns
the plunger 136. As a result, there is no danger of air being trapped
between the head 137 and the inner or left end of the housing 123 to
cause erratic operation of the plunger 136.
During retraction of the legs 14, the air pressure
developed in the cylinder 74 is not sùfficient to overcome the force of
the spring 139 and thus the plunger 136 remains in the position shown
in FIG. 9 until the legs reach their fully retracted position and cause
the pressure in the cylinder to build up. As the legs are extended,
20 the pressure in the cylinder builds up once the feet 12 contact the
ground and start lifting the trailer 11. Accordingly, the driver must
manually hold the knob 130 inwardly to keep the plunger 136 from
closing the valve 81 until the trailer has been lifted to the desired
elevation. As explained previously, however, there is no need for the
driver to tend to the valve 81 once retraction of the legs has been
initiated .
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