Automatic levelling system

A system for automatically levelling a vehicle, such as a recreational vehicle, relative to gravity includes a plurality of extensible jacks, preferably hydraulic, disposed at strategic positions on the bottom of the vehicle. A plurality of switches sense the downward tilting of the vehicle relative to gravity at the strategic positions and produce signals to operate the jacks in accordance with such tilting. The jacks are extended in a particular sequence depending upon the particular directions in which the vehicle is tilted relative to gravity. The jacks become extended only when the hydraulic pressure in a hydraulic circuit exceeds a particular value. Since the rear of the vehicle weighs considerably more than the front, the switches are constructed and are connected in a circuit to resolve any ambiguities in favor of initially operating the jacks at the rear of the vehicle. A delay is preferably provided between the operation of each jack and the operation of the next jack in the sequence so that transients in the levelling of the vehicle from the operation of each jack can be eliminated before the next jack is operated. When the vehicle has been levelled, jacks still not engaging the ground are extended until they engage the ground with a reduced force. When the hydraulic forces in the jacks are less than a particular value while the vehicle is travelling, the hydraulic fluid in the jacks is slowly bled to a reservoir so that hydraulic forces cannot accumulate in the jacks to operate the jacks.

This invention relates to systems for levelling vehicles, such as 
recreational vehicles, relative to gravity and more particularly to 
systems for automatically levelling such vehicles. The invention is 
particularly adapted to be used in vehicles which employ hydraulic jacks 
to level the vehicles relative to gravity. 
Recreational vehicles are now in widespread use to provide families and 
individuals with vacation opportunites at relatively low cost. The 
recreational vehicles allow families and individuals to visit 
out-of-the-way locations of great scenic beauty and to enjoy the scenic 
beauty of these locations at relatively low cost. The vehicles also 
provide such families and individuals with the opportunity to hunt, fish, 
hike and engage in a number of outdoor sports while being assured of 
adequate accommodations and even of home cooking. 
In many locations, the vehicles have to be parked at sites which are not 
level relative to gravity. This results from the fact that the available 
camp sites are often located in rugged terrain. However, in order to 
obtain optimal benefits from such sites, the recreational vehicles should 
preferably be level relative to gravity. For example, when the vehicle is 
level relative to gravity, dishes on tables are stable and people sleeping 
in beds can adopt and maintain comfortable positions. 
Since recreational vehicles are often parked at decidedly non-level sites, 
jacks have been provided to adjust the disposition of the vehicle so as to 
make the vehicle level relative to gravity. These jacks may be either 
hydraulically or electrically operated. The jacks are generally disposed 
at the corners of the recreational vehicle and are attached to the vehicle 
at the underside of the vehicle. The jacks are individually operated to 
adjust the level of the vehicle relative to gravity. As will be 
appreciated, the individual operation of the jacks is time-consuming and 
not always precise. This can be especially disturbing to a family which 
arrives, tired and hungry, at a campsite in the evening and which then has 
to level the vehicle relative to gravity before the evening meal can be 
prepared and served and before the family can start to relax for the 
evening. 
Since the recreational vehicle industry is relatively large, a considerable 
effort has been made, and substantial sums of money have been expended, to 
overcome the problems discussed in the previous paragraph. Some progress 
has actually been made. For example, the jacks in use have been improved 
through the years so that their performance is more reliable than the 
performance of the jacks manufactured and sold a few years ago. In spite 
of such progress, however, major problems still remain. The jacks still 
have to be individually operated, with no assurance that levelling of the 
vehicle relative to gravity can be accomplished in any reasonable period 
of time. 
This invention provides a system for automatically levelling a vehicle 
relative to gravity. The system includes a plurality of extensible jacks, 
preferably hydraulic, disposed at strategic positions at the bottom of the 
vehicle. A plurality of switches sense the downward tilting of the vehicle 
relative to gravity at the strategic positions and produce signals to 
operate the jacks in accordance with such tilting. The jacks are extended 
in a particular sequence depending upon the particular directions in which 
the vehicle is tilted relative to gravity. 
The jacks become extended only when the hydraulic pressure in a hydraulic 
circuit exceeds a particular value. The jacks tilted the greatest relative 
to gravity are initially extended. Since the rear of the vehicle weighs 
considerably more than the front, the switches are constructed and are 
connected in a circuit to resolve any ambiguities in favor of initially 
operating the jacks at the rear of the vehicle. A delay is preferably 
provided between the operation of each jack and the operation of the next 
jack in the sequence so that transients in the movement of the vehicle 
from the operation of each jack can be eliminated before the next jack is 
operated. 
When the vehicle has been levelled relative to gravity, any jacks still not 
engaging the ground are extended until they engage the ground with a 
reduced force. When the hydraulic forces in the jacks are less than a 
particular value and the vehicle is travelling between destinations, the 
hydraulic fluid in the jacks is slowly bled to a reservoir so that 
hydraulic forces cannot accumulate in the jacks to operate the jacks.

In one embodiment of the invention, a system is provided for automatically 
levelling, relative to gravity, a vehicle generally indicated at 10 (FIG. 
1). The vehicle may be a recreational vehicle but it may also be any other 
type of vehicle such as a trailer. Accordingly, as used in the 
specification and claims, the term "vehicle" is intended to mean any type 
of carrier for transporting animate and inanimate objects. 
The levelling of the vehicle 10 relative to gravity is provided by 
extending a plurality of jacks such as jacks generally indicated at 12, 
14, 16 and 18. The jacks are preferably attached to the underside of the 
vehicle 10 at positions near the corners of the vehicle. The jacks 12, 14, 
16 and 18 may be constructed in a conventional manner such as disclosed 
and claimed in U.S. Pat. No. 3,817,493 issued to me on Jan. 18, 1984 for a 
"Hydraulic Jack for Trailers", U.S. Pat. No. 4,165,861 issued to me on 
Aug. 28, 1979, for a "Vehicle Levelling System" or U.S. Pat. No. 4,061,309 
issued to me on Dec. 6, 1977 for a "Vehicle Levelling System and Device 
Therefor". 
Each of the jacks 12, 14, 16, and 18 receives hydraulic fluid initially to 
become pivoted to a vertical position from a horizontal position when the 
jack is disposed against the underside of the vehicle 10 in substantially 
flush relationship with the underside of the vehicle. The jacks are then 
extended downwardly upon a further introduction of hydraulic fluid to the 
jacks. However, as will be appreciated, the jacks may also be constructed 
to become extended or retracted only in the vertical direction without 
first becoming pivoted from the horizontal position to the vertical 
position. 
A hydraulic circuit for one embodiment of the invention is shown in FIG. 2. 
The hydraulic circuit shown in FIG. 2 includes a motor 20 which drives a 
pump 22. A hydraulic line extends from the pump 22 to a relief valve 24 
which is set to operate at a particular pressure such as approximately 
three thousand pounds per square inch (3,000 psi). The relief valve 24 may 
be constructed in a conventional manner. The relief valve 24 operates to 
introduce hydraulic fluid to a reservoir 26 so as to provide a direct 
by-pass from the pump 22 to the reservoir 26 when excessive pressure 
occurs in the line as a result of a malfunction. 
A hydraulic line 28 extends from the pump 22 to a hydraulic pressure switch 
generally indicated at 30. The switch 30 is shown in detail in FIG. 8. The 
valve 30 operates to pass the hydraulic fluid from the pump 22 to a 
hydraulic line 32 when the fluid introduced to the valve 30 has at least a 
particular pressure such as approximately six hundred pounds per square 
inch (600 psi). When the hydraulic pressure introduced to the pressure 
switch 30 is less than six hundred pounds per square inch (600 psi), the 
hydraulic fluid from the line 32 passes to the reservoir 24 through a line 
34. 
The hydraulic fluid in the line 32 is introduced to a valve, generally 
indicated at 36, which is shown in detail in FIG. 7. The valve 36 is 
operated electrically by an electrical switching arrangement generally 
indicated at 38 and shown in FIGS. 4 and 5. The valve 36 operates to pivot 
the jacks 12, 14, 16 and 18 from the horizontal disposition to the 
vertical disposition whenever a master switch is closed to obtain the 
operation of the automatic levelling system and when the automatic 
levelling cycle is started. The output from the valve 36 is connected to 
members 39 in the jacks 12, 14, 16 and 18 for pivoting the extendible arms 
of the jacks from their horizontal positions to their vertical positions. 
Valves generally indicated at 37, 40, 42 and 44 are also included and are 
respectively connected to the jacks 12, 14, 16 and 18 through hydraulic 
lines 50, 52, 54 and 56. The valves 37, 40, 42 and 44 are individually 
activated by the electrical switching arrangement 38 of FIGS. 4 and 5 in 
accordance with the tilting of the recreational vehicle 10 from a 
horizontal level. When the valves 37, 40, 42 and 44 become activated, 
hydraulic fluid passes to the associated jacks 12, 14, 16 and 18 to 
activate the jacks and to produce an extension of arms 48 in the jacks. 
The valves 37, 40, 42 and 44 may be constructed in a manner similar to the 
construction of the valve 36. 
The lines 50, 52, 54 and 56 are respectively connected through check valves 
64, 66, 71 and 70 to a valve 68. The valve 71 may be constructed in a 
manner similar to that of the valve 36. Like the valves 37, 40, 42 and 44, 
the valve 71 is operative to obtain an extension of the jacks 12, 14, 16 
and 18. However, the valve 71 is operative after the vehicle has been 
levelled. At this time, fluid flows through the valve 71 and the check 
valves 60, 62, 64 and 66 to extend to the ground any jacks 10, 12, 14 and 
16 still displaced from the ground. The jacks 10, 12, 14 and 16 are 
extended until they engage the ground with a relatively low force such as 
approximately two hundred pounds per square inch (200 psi). 
A valve generally indicated at 72 is connected between the reservoir 26 and 
the valve 68. The valve 72 constitutes a relief valve to pass the fluid 
from the valve 71 to the reservoir 26 when the pressure of the fluid from 
the valve 71 exceeds a particular limit such as approximately two hundred 
pounds per square inch (200 psi). In this way, the jacks 12, 14, 16 and 18 
are extended to the ground, after the levelling of the vehicle 10 relative 
to gravity, with such a low force that the levelling is not disturbed. The 
relief valve 72 may be constructed in a conventional manner. 
A hydraulic pressure switch 74 may be constructed in a conventional manner. 
The switch 74 may respond to a particular pressure such as approximately 
twenty-five hundred pounds per square inch (2,500 psi). When the switch 74 
responds to such a pressure, it informs a microcomputer in FIG. 12 that 
this pressure limit has been reached. The microcomputer then discontinues 
the extension of the jack providing this hydraulic pressure and produces 
commands to the hydraulic system to obtain the extension of the next jack 
in the sequence after a delay sufficient in time for all transients in the 
movement of the vehicle 10 to disappear. A pressure as high as twenty-five 
hundred pounds per square inch (2,500 psi) may illustratively be produced 
in a jack when the jack has been fully extended or when excessive pressure 
is imposed on the jack for some reason. 
A bleeder valve generally indicated at 78 is also included in the hydraulic 
circuit in FIG. 2 and is connected between the hydraulic line 79 and the 
reservoir 26. The construction of the bleeder valve 78 is shown in detail 
in FIG. 9. The valve 78 is operative at a particular pressure less than 
approximately six hundred pounds per square inch (600 psi) to bleed 
hydraulic fluid from the line 79 to the reservoir 26. This is desirable 
because heat from the vehicle 10, while travelling or from the sun, may 
cause the pressure of the hydraulic fluid in the jack actuators 39 to 
increase to a level sufficient to cause the jacks 10, 12, 14 and 16 to be 
individually pivoted from the horizontal position to the vertical position 
even while the vehicle 10 is travelling between destinations. As will be 
appreciated, such an occurrence may be unfortunate because, at the very 
least, the jacks can be severely damaged when the vehicle travels over a 
bump. By slowly bleeding the fluid through the relief valve 78 below a 
pressure such as six hundred pounds per square inch (600 psi), the 
pressure of the fluid in the jacks can never be built to a value where the 
jacks can be inadvertently pivoted from the horizontal position to the 
vertical position. 
When the vehicle is travelling between destinations, the air bags in the 
vehicle are filled with air to cushion the ride of the vehicle and enhance 
the comfort of the passengers in the vehicle. These air bags are 
schematically illustrated at 83 in FIG. 14. Before the jacks 12, 14, 16 
and 18 are extended vertically, the air in the air bags is exhausted to 
allow the vehicle to settle to the positions where they are supported only 
by the axles of the vehicle. This is accomplished only under the control 
of the microprocessor shown in FIG. 3. 
When the hydraulic system shown in FIG. 2 is to be operated, the motor 20 
drives the pump 22 to produce a flow of hydraulic fluid. The pump 22 then 
introduces hydraulic fluid to the pressure switch 30, which is normally 
closed to prevent fluid from flowing through the switch. When the pressure 
of the hydraulic fluid reaches a preset value such as six hundred pounds 
per square inch (600 psi), the switch 30 is operated to provide for a 
delivery of fluid to the members 39 in the hydraulic jacks 10, 12, 14 and 
16. The jacks are then operated to pivot the extensible arms in the jacks 
from the horizontal to the vertical positions. 
After the extensible arms of the jacks 10, 12, 14 and 16 have been pivoted 
to the vertical positions, the jacks are extended downwardly in a 
particular sequence. This sequence is dependent upon the direction, or 
directions, in which the vehicle 10 is tilted relative to gravity. The 
sequential operation of the jacks occurs through hydraulic circuits 
including the pump 22, the pressure switch 30 and the valves 37, 40, 42 
and 44. The sequential operation of the jacks continues until the vehicle 
has been levelled relative to gravity. The vehicle is generally levelled 
in a relatively short time period such as a period less than one (1) 
minute. A delay is generally provided between the extension of the arm in 
each jack in the sequence and the extension of the arm in the next jack in 
the sequence. This delay is provided to make sure that transients in each 
correction of the vertical disposition of the vehicle relative to gravity 
in one direction, by the operation of any particular one of the jacks 10, 
12, 14 and 16, will not affect such corrections in any other direction 
such as by the operation of any of the other jacks. 
It may sometimes happen that a jack may experience pressures as high as 
twenty-five hundred pounds per square inch (2,500 psi) as it is being 
extended. This may result from an extension of the jack to its full 
length. When this pressure is produced, the switch 74 produces a signal 
which the microcomputer processes. The microcomputer then instructs the 
next jack in the sequence to become extended after a suitable delay to 
eliminate any transients in the movement of the vehicle 10. 
As previously explained, one or more of the jacks 12, 14, 16 and 18 may not 
be engaging the ground even after the vehicle has been levelled. The valve 
68 then becomes operated to extend downwardly the arms of those jacks 
which still do not engage the ground. This occurs by a flow of fluid 
through the appropriate ones of the check valves 64, 66, 68 and 70 and the 
valve 68. Such jacks are then extended downwardly until they engage the 
ground with a pressure such as two hundred pounds per square inch (200 
psi). This extension of the appropriate ones of the jacks 12, 14, 16 and 
18 facilitates the stabilization of the vehicle 10. It also prevents the 
levelling of the vehicle 10 relative to gravity from being upset by the 
downward extension of such jacks, particularly since the jacks are 
extended until they receive only a relatively low pressure. 
After the recreational vehicle has been levelled relative to gravity and 
stabilized, the vehicle 10 is maintained in this position until the 
occupants of the vehicle are ready to travel to another camp site or to 
another destination. At such time, the extendible arms of the jacks 12, 
14, 16 and 18 are retracted and are then pivoted to the horizontal 
positions. The valve 78 is thereafter effective to bleed from the jacks 
12, 14, 16 and 18 any fluid producing a pressure in the jacks of less than 
six hundred pounds per square inch (600 psi). By bleeding the hydraulic 
fluid from the jacks to prevent the pressures of the fluids in the jacks 
from accumulating, the jacks 12, 14, 16 and 18 cannot be inadvertently 
pivoted from the horizontal position to the vertical position while the 
vehicle 10 is travelling between destinations. This prevents the jacks 
from becoming inadvertently damaged. 
The hydraulic circuit includes certain fail-safe features. For example, the 
pump 22 is short circuited to the reservoir 26 through the valve 24 when 
the fluid from the pump exceeds three thousand pounds per square inch 
(3,000 psi). The hydraulic circuitry shown in FIG. 2 also prevents the 
pressure of the fluid in the circuit from exceeding twenty-five hundred 
pounds per square inch (2,500 psi) while the jacks are being extended to 
level the vehicle relative to ground. 
The embodiment of the invention also includes a switching assembly 80 in 
FIGS. 4 and 5. The switching assembly includes a plurality of switches 
such as the switches 82, 84, 86, 88 and 90 disposed on a support member 
91. Each of the switches 82, 84, 86, 88 and 90 may be constructed in a 
similar manner. For example, the switch 88 may be provided with a pair of 
spaced contacts 92 and 94 disposed within an envelope 96. 
A blob 98 of a suitably conductive fluid such as mercury is also disposed 
in the envelope 96. The blob 98 of conductive material is movable into 
engagement with the contacts 92 and 94 in accordance with the tilting of 
the recreational vehicle 10 from a horizontal level. When the blob 98 of 
conductive material engages the contacts 92 and 94, it produces an 
electrical continuity between the contacts. The blob 98 of conductive 
material is moved away from the contacts 92 and 94 when the recreational 
vehicle 10 is tilted in an opposite direction. 
The switches 82, 84, 86 and 88 are disposed on the support member 91 to 
point towards the four corners of the recreational vehicle. For example, 
the switches 82, 84, 86 and 88 respectively point toward the left front, 
the right front, the right rear and the left rear corners of the 
recreational vehicle. Thus, the switch 86 becomes closed when the 
recreational vehicle 10 is tilted downwardly relative to gravity toward 
the left front end of the vehicle and the switch 82 becomes closed when 
the recreational vehicle 10 is tilted downwardly relative to gravity 
toward the right rear end of the vehicle. When the switch 86 becomes 
closed, the associated jack 12 becomes extended to raise the left front 
end of the vehicle from the ground. When the switch 82 becomes closed, the 
associated jack 16 becomes extended to raise the right rear end of the 
vehicle from the ground. 
The switch 90 is disposed between the switches 82 and 84 and is extended in 
a direction parallel to the side walls of the vehicle. The switch 90 
becomes closed when the recreational vehicle 10 is tilted downwardly 
toward the rear. As shown in FIG. 5, the switch 90 is connected in series 
with each of the switches 82 and 84. This means that the rear end of the 
vehicle 10 can be lifted only when both the switch 90 and one of the 
switches 82 and 84 are simultaneously closed. As a practical matter, this 
provides a preference to an initial lifting of the rear of the vehicle (by 
a closure of one of the switches 84 and 86) than an initial lifting of the 
front of the vehicle. This is desirable because the rear of the vehicle is 
heavier than the front of the vehicle. Thus, if there is any ambiguity in 
resolving the particular one of the jacks to be operated first, the 
ambiguity is resolved in favor of operating one of the rear jacks before 
one of the front jacks. 
The hydraulic pressure switch 30 in FIG. 2 is shown in detail in FIG. 8. It 
includes a hollow housing 100 internally threaded as at 102. A plug 104 is 
screwed on the threads 102 and is provided with a bore 106 which 
communicates with the hollow interior of the housing 100. The bore 106 is 
internally threaded as at 108 to receive a hollow threaded fitting 110. 
The housing 100 is provided with an internal shoulder 112 to limit the 
axial movement of a guide 114 toward the right in FIG. 8. The housing 110 
is also provided with an internal wall 116 at a position displaced from 
the guide 114. A helical spring 118 is disposed between the guide 114 and 
the wall 116 under constrained relationship. The guide 114 is provided 
with ports 120 so that fluid in the housing on one side of the guide 114 
can communicate with fluid on the other side of the guide. 
A piston 122 is mechanically coupled to the guide 114 by means of a 
threaded bolt 124. A pair of spaced rings 126 are disposed in sockets in 
the piston 122 at the right end of the piston in FIG. 8 and are 
accordingly movable with the piston. 0-rings 128 are disposed in the 
sockets between the rings 126 and the piston to prevent fluid from leaking 
past the rings. The rings 126 are provided with an external diameter 
corresponding substantially to the internal diameter defining the hollow 
interior of the housing 100. The rings 126 are disposed adjacent ports 130 
in the housing. 0-rings 132 and 134 are disposed on the external surface 
of the housing 100 to seal the housing in an assembly which includes the 
hydraulic pressure switch 30. 
The hydraulic fluid from the pump 22 in FIG. 2 flows into the housing 100 
through the fitting 110. When the pressure of the fluid in the housing 110 
is relatively low, the force on the constrained spring 118 is able to move 
the piston 122 to the left in FIG. 8 to a position where the rings 126 are 
to the left of the ports 130. This prevents any fluid in the housing 100 
from flowing through the ports 130. 
When the pressure of the hydraulic fluid in the housing 100 is greater than 
a particular value such as approximately six hundred pounds per square 
inch (600 psi), this pressure is able to overcome the bias provided by the 
constrained spring 118. The piston 122 is accordingly moved to the 
position shown in FIG. 8. This opens the ports 130 so that fluid is able 
to flow through the ports 130. This fluid is then introduced intitally to 
the line 32 in FIG. 2 for operating the valve 36. This causes the jacks 
12, 14, 16 and 18 to be pivoted from the horizontal position to the 
vertical position. The fluid is then introduced to the jacks 12, 14, 16 
and 18 to extend the jacks sequentially. 
The construction of the valve 36 in FIG. 2 is shown in detail in FIG. 7. In 
the embodiment shown in FIG. 7, a hollow housing 200 made from a suitable 
material such as steel is internally threaded at its right end to receive 
a plug 202. The plug 202 may be made from a relatively soft material such 
as aluminum and is provided with a passage 204. 
A core member 206 made from a suitable member such as steel is fixedly 
disposed in the housing 200. The core member 206 is sealed relative to the 
housing 200 by 0-rings 208. An armature 210 made from a suitable material 
such as steel is also disposed in the housing at substantially the same 
radial level as the core member 206 and in adjacent axial relationship to 
the core member. 
The housing 200, the core member 206 and the armature 210 define a 
compartment 212. A winding 214 is disposed in the compartment 212 and is 
immersed in oil in the compartment. The housing 200, the core member 206 
and the armature 210 define a closed magnetic path through which magnetic 
flux passes when the winding 214 is energized. The flow of this magnetic 
flux causes the armature 210 to be moved to the left. 
A hollow spacer 216 is disposed in the housing 200 at the left end of the 
housing in FIG. 7 to maintain the core member 206 in fixed relationship. A 
guide member 218 is disposed within the spacer 216 for axial movement 
within the spacer. A helical spring 220 is retained in a constrained 
relationship between the guide member 218 and the wall of the housing. 
A dowel 222 extends through the core member 206 from a socket in the guide 
member 218. The dowel 222 extends through a passage 224 in the core member 
206. The dowel 222 contacts a spacer 226 at its right ends. A needle 230 
extends from the spacer 226 through the armature 210 into the passage 204. 
At its left end in FIG. 7, the needle 230 has a flared portion 228 which 
engages the wall of the armature 210. Bearings 232 are disposed on the 
needle 230. The bearings 232 are closely spaced relative to the wall 
defining the passage 204. 
The end of the needle 230 is provided with a tapered configuration, 
preferably relatively gradual, as at 236. In one position of the needle 
230, the tapered portion 236 of the needle 230 cooperates with a valve 
seat 238 to define a closed valve. The valve seat 238 is defined by a 
tapered shoulder in the wall defining the passage 204. The taper of the 
shoulder defining the valve seat 238 is preferably steeper than that 
provided on the end 236 of the needle 230 to facilitate valve closure. 
The needle 230 is displaced from the wall defining the passage 204 to 
define a channel 240. An aperture 242 is disposed in the plug 202 at 
positions adjacent the channel 240 to communicate with the channel. 
0-rings 246 and 248 are disposed at spaced positions on the external wall 
of the housing to seal the housing in the assembly which includes the 
housing. 
During the time that the solenoid winding 212 is not being energized, the 
spring 220 acts through the guide member 218 on the dowel 222 to move the 
dowel, the spacer 226 and the needle 230 toward the right in FIG. 7. This 
causes the valve defined by the tapered portion 236 of the needle and the 
valve seat 238 to become closed. When this valve is closed, fluid cannot 
flow through a hydraulic circuit including the aperture 242 and the 
passage 204. 
The solenoid winding 212 is energized when the extensible arms of the jacks 
12, 14, 16 and 18 in FIGS. 1 and 2 are to be pivoted from the horizontal 
position to the vertical portion for subsequent extension. When the 
solenoid winding 212 is energized, the flow of magnetic flux through the 
magnetic circuit defined by the housing 200, the core member 206 and the 
armature 210 causes the armature to be moved to the left in FIG. 7. The 
movement of the armature 210 to the left causes the armature to act upon 
the flared portion 228 of the needle 230 to move the spacer 226 and the 
dowel 222 to the left in FIG. 7. The dowel 222 acts upon the guide member 
218 to compress the spring 220. 
When the armature 210 is moved to the left, the fluid in the channel 240 
acts upon the needle 230 to move the needle to the left in FIG. 7. This 
displaces the tapered end 236 of the needle 230 from the valve seat 238 so 
that fluid is able to flow through the hydraulic circuit including the 
aperture 242 and the passage 204. The fluid flowing from the passage 204 
acts upon the jacks 12, 14, 16 and 18 to pivot the extensible arms of the 
jacks from their horizontal positions to their vertical positions. 
The apparatus shown in FIG. 7 and disclosed above has certain important 
advantages. It provides for a positive opening and closing of the valve 
formed by the tapered end 236 of the needle 230 and the valve seat 238. 
This results in part from the provision of the solenoid winding 212 and 
the provision of the magnetic circuit formed by the housing 200, the core 
member 206 and the armature 210. It further results from the force exerted 
by the fluid in the channel 224 against the needle 230. 
The apparatus shown in FIG. 7 and disclosed above also has other important 
advantages. The fluid in the aperture 242 communicates through the 
bearings 232 and then acts against the spring 220, through the action of 
the dowel 222, tending to compress the spring. This means that the 
magnetic force generated by energizing the solenoid winding 214 to open 
the valve is reduced rather than increased as in a conventional valve when 
the pressure of the hydraulic fluid is increased in the aperture 242. 
Another advantage occurs as the pressure of the fluid in the passage 204 
increases to a value of approximately forty-five hundred pounds per square 
inch (4,500 psi). When this occurs, the force acts against the needle 230, 
the spacer 226, the dowel 222 and the guide member 218 to compress the 
spring 220. This allows fluid to pass through the valve defined by the 
seat 238 and the needle 230. The valve thus serves as a safety valve to 
protect the jacks in the event that the vehicle 10 is moved. 
There are other advantages to the apparatus of FIG. 7. These advantages 
result from the fact that the valve defined by the tapered end 236 of the 
needle 230 and the valve seat 238 is closed gently, and without any 
chattering, when the solenoid winding 212 is de-energized. This results 
from the relative tapers on the portion 236 of the needle 230 and the 
valve seat 238. It also results in part from the formation of the valve 
seat 238 from a soft material such as aluminum. It further results from 
the formation of the dowel 222, the spacer 226 and the needle 230 as 
separate parts. By providing such separate parts, the movements of the 
needle 230 are damped relative to any movements imparted to the dowel 222. 
This is particularly true since the parts are disposed in oil. The 
dampened movements of the needle 230 also result from the action of the 
flared portion 228 of the needle 230 on the armature 210 in moving the 
armature to the right in FIG. 7. Since the armature 210 is a relatively 
heavy member, its inertia causes it to move to the right independently of 
the movement of the needle 230. As a result, the tapered end 236 of the 
needle 230 is able to engage the valve seat 238 gently without producing 
any damage in these members. 
FIG. 9 illustrates in detail the construction of the bleeder valve 78 shown 
in FIG. 2. The valve 78 includes a housing 300 internally bored to define 
a channel 302 at the left end in FIG. 9 and an enlarged chamber 318 at the 
right end in FIG. 9. The channel 302 is shaped at the left end in FIG. 9 
to define a seat 304. The seat 304 is preferably tapered. A tapered 
shoulder 306 is also provided between the channel 302 and the chamber 318 
to provide a continuity between the channel and the chamber. The internal 
bore of the channel 302 is shaped to define a valve seat 307. 
A plunger 308 is disposed in the channel 302 for axial movement and is 
retained within the channel 302 by the seat 304. The plunger 308 has a 
ball 310 at the left end in FIG. 9. The ball 310 cooperates with the valve 
seat 307 to define a valve. In the position of the ball 310 in FIG. 9, the 
valve is open. The ball 310 is provided with a relatively large diameter 
compared to the diameter of the channel 302 to limit the rate at which 
fluid is able to flow through the channel when the valve defined by the 
ball 310 and the valve seat 304 becomes opened. When the plunger is moved 
to the right in FIG. 9, the valve becomes closed. 
The plunger 310 has an enlarged sleeve portion 312 and also has a tapered 
portion 314 which is disposed between the reduced portion at the left end 
of the plunger and the sleeve portion 312. The taper of the portion 314 is 
adjacent the shoulder 306 and is more gradual than that of the shoulder 
306 in the channel 302. 
A retaining ring 316 is disposed in the enlarged chamber 318 of the housing 
300 adjacent the sleeve 312 for movement with the plunger. The retainer 
ring 316 abuts a snap ring 320 which is disposed on the periphery of the 
sleeve 312. The retainer ring 316 provides for an axial movement of the 
snap ring with the retainer ring. A snap ring 322 is fixedly disposed in 
the chamber 318 in spaced relationship to the ring 6. A helical spring 324 
is disposed on the sleeve 312 in a constrained relationship between the 
snap rings 316 and 322. 
The spring 324 normally biases the snap ring 320 and the retainer ring 316 
toward the left in FIG. 9. In this relationship, the valve defined by the 
valve seat 307 and the ball 310 is open when the force of the spring is 
greater than the force of the fluid acting on the ball 310 at the left end 
in FIG. 9. As a result, fluid is able to flow the channel 302 and the 
chamber 318. This flow of fluid prevents any build-up of pressure in the 
jacks 12, 14, 16 and 18 during the time that the jacks are in their 
horizontal positions such as when the vehicle 10 is travelling between 
destinations. 
When the force of the fluid acting on the ball 310 is greater than a 
particular value such as approximately six hundred pounds per square inch 
(600 psi), the force of the fluid exceeds the bias of the spring 324. This 
causes the plunger 308 to move to the right in FIG. 9 so as to close the 
valve defined by the valve seat 307 and the ball 310. Fluid is then unable 
to flow through the the channel 302 and the chamber 318. This prevents the 
bleeder valve 78 from acting to bleed fluid during the time that the 
hydraulic circuitry shown in FIG. 2 is acting to pivot the jacks 12, 14, 
16 and 18 from the horizontal position to the vertical position and during 
the time that the jacks are being extended. 
FIG. 6 is a side view of a jack which may be used in g the embodiment 
discussed above. FIG. 6 corresponds substantially to FIG. 4 of my U.S. 
Pat. No. 4,165,861. Assuming a support assembly 350 to be in an upper 
storage position as shown in FIG. 6, the outer end of a plunger 352 will 
react against a roller 354 as the plunger is extended from a cylinder 356. 
Such a reaction will cause the support assembly 350 to rotate around 
pivots 358 while the outer end of the plunger 352 rotates around the 
roller 354. When the pivotal movement of the plunger 352 has been 
completed, a plunger 360 is extended upon introduction of a suitable 
hydraulic fluid. Such extension is limited by abutment between a shoulder 
366 in the interior wall of a cylinder 368 and a stop collar 370 carried 
on the plunger 360. A foot or pad 380 serves to provide a relatively large 
flat surface for contact with the ground. 
FIG. 3 schematically shows an electrical system generally indicated at 400 
and including a microprocessor 402, for operating in the proper sequence 
the different mechanisms discussed above. The system shown in FIG. 3 also 
includes a master switch 404 and an "Automatic Level" switch 406 for 
controlling the operation of the system. When the master switch 
404 and the "Automatic Level" switch 406 are closed as first steps 
(indicated as "A" in FIG. 3) in the sequence, the microprocessor 402 is 
operative to energize the motor 20 in FIG. 2, as indicated by a letter "B" 
in FIG. 3. The motor 20 then operates the pump 22 to obtain a flow of 
fluid through the hydraulic circuit shown in FIG. 3. The solenoid in the 
valve 36 is then energized, in accordance with the processing of data by 
the microprocessor 402, to obtain a flow of fluid through the jacks 12, 
14, 16 and 18 to pivot the extensible arms of the jacks from the 
horizontal positions to the vertical positions. This is indicated by a 
letter "C" in FIG. 3. As previously disclosed, however, this step may be 
eliminated if the jacks are only vertically extensible without first being 
pivoted from the horizontal position to the vertical position. 
The microprocessor 402 is then operative to obtain an exhaustion of the air 
in the air bags 83 for (FIG. 14) cushioning the ride of the vehicle 10. 
This is indicated by a line 408 extending from the microprocessor 402 to a 
box 410 designated as "Exhaust Air From Air Bags in Vehicle 10". It is 
also indicated by a letter "D" adjacent the line 408 to show that this is 
the next step in the sequence after the pivoting of the jacks from the 
horizontal position to the vertical position. 
The solenoids in the valves 37, 40, 42 and 44 are then energized in a 
particular sequence to level the recreational vehicle relative to gravity. 
This is indicated by a letter "E" in FIG. 3. The sequence of energizing 
the solenoids in the valves 37, 40, 42 and 44 is dependent upon the 
particular direction or directions in which the recreational vehicle is 
tilted downwardly relative to gravity. As previously described, preference 
is given by the switching circuitry shown in FIGS. 4 and 5 to operate the 
jacks at the rear of the vehicle before the jacks at the front of the 
vehicle in case of any ambiguity in the sequence of operating the jacks 
because the rear of the vehicle is heavier than the front of the vehicle. 
By raising the rear of the vehicle before the front of the vehicle, only a 
minimal extension may have to be made in the jacks at the front of the 
vehicle in order to level the vehicle. 
Although preference is given to levelling the rear of the vehicle 10 over 
levelling the front of the vehicle in case there is any ambiguity, the 
sequence of operating the jacks 12, 14, 16 and 18 is actually dependent 
upon the direction in which the vehicle is tilted. The first one of the 
jacks 12, 14, 16 and 18 to be levelled is that one which is skewed the 
most from the direction of gravity. This selection is made by the 
microprocessor 402 in accordance with the closure of the switches shown in 
FIGS. 4 and 5. Generally one of the jacks adjacent such first selected 
jack is the next to be selected since it is the jack most skewed from the 
direction of gravity after the corner of the vehicle corresponding to the 
positioning of the first selected jack has been made level relative to 
gravity. 
When the second one of the selected jacks has been extended sufficiently to 
make the corresponding corner of the vehicle level relative to gravity, 
the third jack is then operated. This third jack is adjacent generally to 
the second selected jack in the same direction of rotation as from the 
first jack to the second jack. The fourth jack selected for extension is 
in turn generally adjacent to the third selected jack in the same 
direction of rotation as from the second jack to the third jack. 
It may be that the levelling operation relative to gravity is not yet 
consummated after the four (4) jacks have been operated in sequence. If 
such levelling relative to gravity is not yet consummated, the four jacks 
are again operated in the same sequence until the levelling has been 
consummated. Generally the levelling relative to gravity is consummated 
after only one sequence of operating the different jacks or, at most, 
after only two (2) sequences of operating the different jacks. As will be 
appreciated, the operation of the jacks through only one sequence or 
through more than one sequence is controlled by the microprocessor 402. 
Thus, although the operation of the solenoids in the valves 38, 40, 42 and 
42 is indicated by the single letter "E" in FIG. 3, it will be appreciated 
that the operation of those valves may occur through a number of steps, 
all under the control of the microprocessor 402. 
After each operation of one of the jacks 12, 14, 16 and 18, a delay is 
provided by the microprocessor 402 before the next one of the jacks in the 
sequence is operated. This is indicated by delays 412 and 414 in FIG. 3. 
These delays are provided so that any transients in the movement of the 
vehicle 10 as a result of the operation of each jack will be dissipated 
before the next one of the jacks in the sequence is operated The delay is 
provided for each jack after the operation of the jack is interrupted by 
the conversion of the associated switch in FIGS. 4 and 5 from a closed 
state to an open state. It will be appreciated that the delays 412 and 414 
are shown in FIG. 3 as being associated with the microprocessor 402 since 
the delays may be provided as a result of the programming of the 
microprocessor 414. 
The microprocessor 402 senses when the vehicle 10 is levelled relative to 
gravity because all of the switches in FIGS. 4 and 5 are simultaneously 
opened. When the vehicle 10 is levelled relative to gravity, the 
microprocessor 402 causes the solenoid in the valve 71 to be energized 
after a suitable time delay. This produces an operation of all of the 
jacks 12, 14, 16 and 18 still not contacting the ground. Such jacks are 
operated until they engage the ground. Such operation is indicated by a 
letter "F" in FIG. 3. In this way, the stability of the vehicle 10 is 
enhanced without affecting the levelling previously provided in the 
vehicle. 
When it is desired to prepare the vehicle 10 for departure from a campsite, 
the "Master" switch 404 and an "Automatic Retract" switch 420 are 
operated. When the "Master" switch 404 is on and the "Automatic Retract" 
switch 420 is closed, the microprocessor 402 causes the valves 36, 37, 40, 
42 and 44 so that the fluid in the jacks 12, 14, 16 and 18 is returned to 
the reservoir 26 and the extendible arms in the jacks become retracted. 
Such retraction of the jacks 12, 14, 16 and 18 can occur simultaneously or 
in sequence. The retraction of the jacks 12, 14, 16 and 18 and the 
pivoting of the jacks to the horizontal position occur because of the 
force of the retracting springs on the jacks. 
It will be appreciated that the system shown in FIG. 2 can be operated 
manually as well as automatically. This can be accomplished by providing a 
manually operated switch for each jack and by manually operating the 
switch until an indication is provided on a visual sensor that the vehicle 
10 has been levelled at the position on the vehicle corresponding to the 
position where the jack is coupled to the vehicle. However, when the 
"Automatic Level" switch 406 is operated, the automatic levelling of the 
vehicle 10 has a priority over any manual levelling of the vehicle 10. 
As will be appreciated, levelling of a recreational vehicle can be provided 
by controlling the vertical disposition of three (3) spaced points 
relative to gravity. For example, the levelling of a recreational vehicle, 
generally indicated at 500 in FIG. 10, relative to gravity can be 
controlled by three jacks generally indicated at 502, 504 and 506. The 
jacks 502, 504 and 506 are disposed at spaced positions on the vehicle at 
the underside of the vehicle. The jacks 504 and 506 may be disposed at the 
opposite rear ends of the vehicle 500 and the jack 502 may be disposed at 
the front of the vehicle at a position intermediate the front ends of the 
vehicle. Actually, the use of only three (3) jacks should be theoretically 
superior to the use of four (4) jacks as in the previous embodiment shown 
in FIGS. 1 through 9 since an object can be levelled by levelling only 
three (3) spaced positions on the object. The jacks 504 and 506 are 
disposed at the opposite rear ends of the vehicle 500 since the rear end 
of the vehicle is heavier than the front of the vehicle. 
Since the length of the vehicle 500 is generally significantly longer than 
its width, the jacks 502, 504 and 506 do not define an equilateral 
triangle but only an isosceles triangle. This results from the fact that 
the distance between the jacks 504 and 506 is considerably less than the 
distance between the jacks 502 and 506 or between the jacks 502 and 504. 
In view of the particular geometry involved, problems may arise in the 
priorities of operating the jacks 502, 504 and 506 if the recreational 
vehicle should be tilted downwardly toward the rear relative to gravity. 
Any ambiguities in the priorities of operating the jacks 502, 504 and 506 
can be resolved by providing a switching arrangement such as shown in 
FIGS. 11 and 12. This arrangement includes a support member 510 on which a 
plurality of switches 512, 514 and 516 are disposed. The switches 512, 514 
and 516 may be mercury switches and may be constructed in a manner similar 
to that disclosed above for the switches shown in FIGS. 4 and 5. The 
switches 512, 514 and 516 may be respectively disposed at positions to 
obtain an operation of the jacks 502, 504 and 506 when they are closed. 
For example, when the switch 512 is closed, it indicates that the vehicle 
500 is tilted downwardly in the forward direction relative to gravity. 
This causes the jack 502 to be extended so that the front end of the 
vehicle 500 becomes raised relative to gravity. 
A switch 518 is also disposed on the member 510 in addition to the switches 
512, 514 and 516. The switch 518 is disposed opposite the switch 512 and 
is connected in parallel with the switch 514 (FIG. 12). The switch 518 may 
also be a mercury switch. The switch 518 is closed when the recreational 
vehicle 500 is tilted downwardly toward the rear. When the switch 518 is 
closed, the jack 506 is extended to tilt the right rear end of the vehicle 
upwardly. The jack 504 can then be extended to tilt the left rear end of 
the vehicle 500 upwardly. In this way, the inclusion of the switch 518 and 
the connection of this switch in parallel with the switch 514 provide a 
resolution as to any ambiguities in the sequence of operating the jacks 
when the rear end of the vehicle 500 is tilted downwardly. 
FIG. 13 shows a hydraulic circuit for operating the jacks 502, 504 and 506 
in sequence. The hydraulic circuit shown in FIG. 13 is similar to the 
circuit shown in FIG. 2 except for a limited number of differences. For 
example, only the three jacks 502, 504 and 506 are included. The extension 
of these jacks is respectively controlled by three valves generally 
indicated at 530, 532 and 534. Each of these valves may be constructed in 
a manner similar to that shown in FIG. 7. The hydraulic circuit shown in 
FIG. 13 also includes a pressure switch generally indicated at 536 and 
corresponding to that shown in FIG. 8. 
As will be seen in FIG. 13, no valve is included to pivot the jacks 502, 
504 and 506. This results from the fact that the jacks 502, 504 and 506 
are not pivotable in this embodiment but are operative only to become 
extended and retracted. Hydraulic jacks of this type are well known in the 
prior art. 
Although this invention has been disclosed and illustrated with reference 
to particular embodiments, the principles involved are susceptible for 
uses in numerous other embodiments which will be apparent to persons 
skilled in the art. The invention is, therefore, to be limited only as 
indicated by the scope of the appended claims.