Landing gear control system for trailers

A landing gear system for a trailer is described. The landing gear system includes two jacks, each with a first tubular body in which a second tubular body is telescopically mounted, a hydraulic chamber and a pneumatic chamber. The system includes a hydraulic fluid reservoir, a pneumatic fluid source, a pneumatic manifold in pneumatic fluid communication with the pneumatic source and in pneumatic fluid communication with said hydraulic reservoir and a hydraulic manifold in hydraulic fluid communication with the hydraulic reservoir. Pneumatically operated hydraulic pumps are included, along with a central control mechanism attached to the pneumatic manifold and disposed to simultaneously control pneumatic flow into the pneumatic chambers of the jacks and to pneumatically operated hydraulic pumps. Separate pneumatically operated hydraulic valve are provided to individually control hydraulic flow from the jacks.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to semi-trailer landing gear extension and retraction mechanisms, and more particularly to a pneumatic and hydraulic control mechanism that promotes coordinated extension and retraction of landing gear legs.

2. Description of the Prior Art

Many semi-trailers have front landing gear for support of the front of the trailer when the tractor is detached. Such landing gear generally has two spaced-apart, telescoping or Jack-type landing gear legs which extend downwardly from the bed of the trailer.

Traditionally, each leg is operatively attached to a screw and follower or a rack and pinion gear arrangement which is driven by a landing gear drive shaft extending between the legs. The drive shaft controls extension or retraction of the legs depending on the direction in which it is rotated. Most commonly, a hand operable crank is attached to the landing gear drive shaft. Manual rotation of the crank via a crank handle causes extension and retraction of the landing gear. Manually operated jack structures, however, are often difficult to use, require much time for their operation and expose the operator to potential injuries as he is positioned next to the trailer while turning the crank to raise or lower the landing gear.

More recently, landing gear systems have been provided with powered devices in order to raise and lower the landing gear. Some of these powered devices have been pneumatically powered. Typically, such pneumatic devices require a complex control and piping system to receive pressurized air for the motion actuators to rotate the crank shaft of the gear reduction assembly to raise and lower the landing gear. One class of prior art pneumatic devices has utilized pneumatic impact motors to drive the landing gear. Of course, those skilled in the art will understand that due to their pulsating drive mechanism, such pneumatic impact motors are not conducive to the desired smooth operation of raising and lowering the landing gear legs, especially in combination with gear reduction boxes.

Another class of prior art pneumatic mechanisms dispenses with the gearing system of traditional landing gear and utilizes a pneumatic bladder or chamber within each leg to telescope the landing gear.

Piston driven hydraulic landing gear devices are also known in the prior art. Similar to the pneumatic air bladder/chamber system referenced above, such devices replace traditional drive shaft/gearing systems and utilize hydraulic pistons to drive the landing gear. One drawback to hydraulic pistons is that they do not provide the same positive holding as provided by a gearing arrangement. Power failure or loss of fluid pressure could cause failure and collapse of the landing gear. As with the pneumatic systems, typically, such hydraulic devices require a complex control and piping system.

Moreover, with respect to either pneumatic or hydraulic bladder/chamber systems, it has been found that it is desirable to utilize two smaller pumps to provide pressurized fluid for actuation of the system. In the prior art, such pumps are typically located adjacent their respective jacks to pump hydraulic fluid from a reservoir located adjacent the jack to a chamber within the telescoping leg of the jack, and, as mentioned above, require complex control and piping systems. It has been found that such systems, in particular those requiring a significant amount of piping, couplings and the like, are readily subject to wear and/or damage by virtue of the operating environment to which they are exposed, i.e., high vibration, exposure to road debris, etc. Moreover, such systems have individual controls for the respective jacks. Such a control system promotes damage to the system and trailer frame, when the jacks are not correctly synchronized during raising and lowering, thereby causing twisting of the trailer frame.

In addition, such systems are generally large, cumbersome and permanently installed as an integrated part of the drive system, and do not lend themselves to retrofitting on trailers have pre-existing landing gear.

SUMMARY OF THE INVENTION

The present invention provides a landing gear system whereby telescoping jacks of the landing gear are driven by both hydraulic and pneumatic fluids, the flow of which is controlled by centrally located pumps, a centrally located pneumatic manifold, a centrally located hydraulic manifold and, preferably, a single control mechanism. The system utilizes a single oil reservoir that is also located adjacent the manifolds and pumps.

The system eliminates much of the piping and couplings of the prior art. Moreover, the system inhibits operator induced twisting of the trailer frame due to uneven raising and lowering of the two jack legs. Finally, the system is more readily retrofitted for use on existing trailers because of the centrally located pump, manifold and control system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1adepicts a conventional drive-shaft driven landing gear assembly10of the prior art. As can be seen in the view ofFIG. 1a, the landing gear10has a drive shaft12which passes through the upper ends of a pair of telescoping legs14. Each leg14has an outer tubular body16in which an inner tubular portion18is telescopically received. Pivotally mounted feet, wheels or pads20attach to the distal end of each inner tubular portion18. Conventional gear mechanisms (not shown) within outer tubular body16cause the inner tubular portion18to raise or lower, depending upon the direction of rotation of the drive shaft12. A gear reduction box24may also be provided to assist in transfer of power to the drive shaft12.

FIG. 1bdepicts a hydraulically driven landing gear assembly30of the prior art. As can be seen in the view ofFIG. 1b, the landing gear30includes a pair of telescoping legs32, each of which has a hydraulic reservoir34disposed on top of its respective leg32. Each leg32is further provided with a pneumatically driven oil pump35adjacent the oil reservoir34and an oil manifold disposed37on the leg32to supply oil to its respective leg32. Each leg32has a respective toggle switch36to released compressed air to the pump35, the reservoir34and internally to leg32from an air reservoir38. Finally, each leg includes manual knob valves39to permit flow from the respective legs32back into the respective oil reservoirs34.

With reference toFIG. 2, a landing gear system40of the invention is shown. Generally, landing gear system40includes a central control module42and a pair of telescoping legs44. Each telescoping leg generally comprises an outer tubular member46with an inner tubular member48slidingly disposed therein. Each inner tubular member48may include a foot50.

Each leg44also includes a piston52, hydraulic gaskets54, pneumatic gaskets56, a piston rod or plunger58, a hydraulic fluid port60, a hydraulic fluid chamber62, a pneumatic fluid port64and a pneumatic fluid chamber66. The hydraulic fluid port60is in fluid communication with the hydraulic fluid chamber62which is in fluid communication with the upper pressure surface of piston52. The pneumatic fluid port64is in fluid communication with the pneumatic fluid chamber66which is in fluid communication with the lower pressure surface of piston52. Piston rod58is attached to the proximal end of inner tubular member46, and piston52is axially movable within tube46to extend or retract piston rod58(and hence, tube48) under pressure applied to the respective upper and lower pressure surfaces of piston52. Hydraulic fluid port60may include a flow control or check valve to restrict flow of hydraulic fluid from chamber62back into hydraulic reservoir82.

With reference toFIGS. 3-5, control module42generally comprises a hydraulic manifold70, a pneumatic manifold72, a central control mechanism76and pneumatically controlled hydraulic pumps or intensifiers78,80. In certain preferred embodiments, control module42also comprises air operated oil control valves81. Control module42is preferably disposed in an enclosure83to protect the components of control module42from the environment.

A hydraulic reservoir82, containing a hydraulic fluid, is positioned adjacent control module42and is in fluid communication with hydraulic manifold70. In one embodiment, the hydraulic fluid is oil.

Likewise, a pneumatic source85is in fluid communication (not shown) with pneumatic manifold72. In one embodiment, pneumatic source85is a compressed air reservoir. In another embodiment, pneumatic source85is an air compressor.

Referring toFIG. 6, pneumatic manifold72is provided with an air supply inlet90in fluid communication with a first internal passage92. Manifold72is further provided with a second internal passage94and a third internal passage96. Central control mechanism76(shown inFIGS. 3-5) is operable to selectively fluidly connect either second internal passage94or third internal passage96with first internal passage92to supply pneumatic fluid thereto. In one embodiment, central control mechanism76is a self-centering switch, such as a spring centered joy stick, that has a first position, a second neutral position and a third position. Those skilled in the art will understand that such a self-centering joy stick is disposed to return to the second neutral position when not under a force urging the lever to the first or third positions. Moreover, in the neutral position, neither the second internal passage94nor the third internal passage96is fluidly connected to the first internal passage92.

In the first position, central control mechanism76fluidly couples first internal passage92to third internal passage96in order to extend both tubes48. In the third position, central control mechanism76fluidly couples first internal passage92to second internal passage94in order to retract both tubes48. As discussed above, central control mechanism76controls the extension or retraction of both tubes48in a synchronized manner so as to avoid frame twisting.

Third internal passage96is likewise in fluid communication with a first pneumatic outlet98, a second pneumatic outlet100and a third pneumatic outlet102.

Referring back toFIGS. 3-5, first pneumatic outlet98is in fluid communication with hydraulic reservoir82to provide head pressure to hydraulic fluid disposed therein. Second pneumatic outlet100is in fluid communication with the oil pump78and is disposed to supply a pneumatic working fluid thereto in order to drive pump78. Likewise, third pneumatic outlet102is in fluid communication with oil pump80and is disposed to supply a pneumatic working fluid thereto in order to drive pump80.

With reference toFIG. 7, hydraulic manifold70includes a first internal passage104in fluid communication with hydraulic source82and a second internal passage106in fluid communication with hydraulic source82. Each of the first internal passages104,106is in fluid communication with a hydraulic fluid port108. Each manifold hydraulic fluid port108is in fluid communication with the hydraulic fluid port60of one of the hydraulic chambers62.

Each hydraulic pump78,80is mounted on the hydraulic manifold70at79and is disposed to pump hydraulic fluid from hydraulic reservoir82via passage104,106to hydraulic chamber62via ports108so as to provide a head pressure to the hydraulic chamber62. Each hydraulic port108may include a check valve109to control hydraulic flow therethrough.

Preferably, hydraulic reservoir82is in direct fluid communication with hydraulic manifold70so as to obviate the need for external piping between manifold70and reservoir82.

Hydraulic manifold70may further include a third passage110and a forth passage112, each of which receives an air operated oil control valve81to control the flow of hydraulic fluid therethrough. Although it is desirable to raise legs48in a synchronized manner utilizing central control mechanism76, those skilled in the art will appreciate that hydraulic legs tend to wear at different rates. A central control mechanism76that operates to retract both legs48simultaneously may result in twisting of the trailer frame. As such, to the extent legs48are not synchronized in their retraction or are otherwise extended or aligned to different degrees, valves81may be utilized to override central control mechanism76so as to permit hydraulic fluid flow from only one hydraulic chamber62back into reservoir82as necessary to individually adjust the relative positions of the two legs48until their relative extended positions are the same (at which point, central control mechanism76may thereafter be utilized to continue retraction of both legs48). In other words, air operated oil control valves81permit control of each leg48separately, while the particular aforementioned central control mechanism76permits control of each leg simultaneously.

In another embodiment of the invention, central control mechanism76has a forth and fifth position. In such an embodiment, central control mechanism76may replace air operated oil control valves81. In the fifth position, central control mechanism76permits hydraulic fluid flow from only one hydraulic chamber62back into reservoir82as necessary to adjust the relative positions of the two legs48until their relative extended positions are the same. Likewise, in the sixth position, central control mechanism76permits hydraulic fluid flow from only the other hydraulic chamber62back into reservoir82as necessary to adjust the relative positions of the two legs48until their relative extended positions are the same.

Check valves, or similar one-way flow devices, may be utilized in one or both manifolds, as well as, or alternatively, in each jack or telescoping mechanism to ensure that fluid, particularly pressurized fluid, does not backflow through a particular fluid path.

In operation, to lower legs44by telescopingly extending tube48relative to tube46, central control mechanism76is moved into the first position. In this first position, a pneumatic pressure head is applied, via first pneumatic outlet98, to hydraulic fluid within reservoir82, so as to cause the hydraulic fluid to quickly flood into chambers62, applying pressure to piston52and thereby rapidly extending tubes48until they meet resistance, i.e., the ground. At this point, pumps78,80continue to pump highly pressurized hydraulic fluid into chambers62so as to continue to extend tubes48against the load of the trailer. Once the legs44have been telescopically extended as desired, central control mechanism76may be released, at which point it will automatically come to rest in the second or neutral position.

To raise legs44by telescopingly retracting each tube48relative to tube46, central control mechanism76is moved into the third position. In this third position, pneumatic fluid such as air is introduced into air chambers66via air inlets64of legs44. The air pressure urges pistons52axially along tubes46, thereby pushing the hydraulic fluid in chambers62back into hydraulic reservoir82. To the extent legs44include hydraulic fluid flow control valves, the valves may be opened to allow the weight of the trailer to urge the hydraulic fluid of chambers62back into hydraulic reservoir82until the trailer rests on a support (such as a fifth wheel), at which point the pneumatic air within air chambers66will continue to cause the retraction of tubes46.

To the extent legs44have worn at different rates resulting in their respective tubes48being extended to different degrees, air operated oil control valves81can be utilized to synchronize the two tubes48.

Those persons of ordinary skill in the art will appreciate that while the foregoing invention has been described in the context of landing gear having two legs, it may also be utilized for single leg jacks or other telescoping mechanisms.

In one exemplary aspect, the present disclosure is directed to a landing gear system that includes a first jack comprising a first tubular body in which a second tubular body is telescopically mounted, a hydraulic chamber and a pneumatic chamber; a second jack comprising a first tubular body in which a second tubular body is telescopically mounted, a hydraulic chamber and a pneumatic chamber; a hydraulic fluid reservoir; a pneumatic fluid source; a pneumatic manifold in pneumatic fluid communication with the pneumatic source and in pneumatic fluid communication with said hydraulic reservoir; a hydraulic manifold in hydraulic fluid communication with the hydraulic reservoir; a first pneumatically operated hydraulic pump in pneumatic fluid communication with the pneumatic manifold and in hydraulic fluid communication with the hydraulic manifold; a second pneumatically operated hydraulic pump in pneumatic fluid communication with the pneumatic manifold and in hydraulic fluid communication with the hydraulic manifold; a central control mechanism attached to the pneumatic manifold and disposed to control pneumatic flow into the pneumatic chambers of the first and second jack, the first and second pneumatically operated hydraulic pump and the hydraulic reservoir; and a first pneumatically operated hydraulic valve separate from the central control mechanism, said first pneumatically operated hydraulic valve disposed to control hydraulic fluid flow from the hydraulic chamber of the first jack back into the hydraulic fluid reservoir.

In one exemplary aspect, the present disclosure is directed to a landing gear system for a trailer, the system including a first jack having a first tubular body in which a second tubular body is telescopically mounted, a hydraulic chamber and a pneumatic chamber; a second jack having a first tubular body in which a second tubular body is telescopically mounted, a hydraulic chamber and a pneumatic chamber; a hydraulic fluid reservoir; a pneumatic fluid source; a pneumatic manifold in pneumatic fluid communication with the pneumatic source and in pneumatic fluid communication with said hydraulic reservoir, said pneumatic manifold comprising first, second and third internal passages and an air supply inlet in fluid communication with a first internal passage; a hydraulic manifold in hydraulic fluid communication with the hydraulic reservoir, said hydraulic manifold comprising a first internal passage in fluid communication with the hydraulic reservoir, a second internal passage in fluid communication with hydraulic reservoir, a first port in fluid communication with the first internal passage and a second port in fluid communication with the second internal passage, wherein the first port of the hydraulic manifold is in fluid communication with the hydraulic chamber of the first jack and the second port of the hydraulic manifold is in fluid communication with the hydraulic chamber of the second jack; a first pneumatically operated hydraulic pump in pneumatic fluid communication with the pneumatic manifold and in hydraulic fluid communication with the hydraulic manifold; a second pneumatically operated hydraulic pump in pneumatic fluid communication with the pneumatic manifold and in hydraulic fluid communication with the hydraulic manifold; a central control mechanism attached to the pneumatic manifold and disposed to control pneumatic flow into the pneumatic chambers of the first and second jack, the first and second pneumatically operated hydraulic pump and the hydraulic reservoir, wherein the central control mechanism is a self-centering mechanism having a first position, a second position and a third position, wherein the central control mechanism is disposed to self-center to the second position, wherein the central control mechanism when in first position permits pneumatic fluid communication between first internal passage and third internal passage of the pneumatic manifold and when in the third position, permits pneumatic fluid communication between first internal passage and the second internal passage of the pneumatic manifold; and a first valve disposed to control hydraulic fluid flow from the hydraulic chamber of the first jack back into the hydraulic fluid reservoir and a second valve disposed to control hydraulic fluid flow from the hydraulic chamber of the second jack back into the hydraulic fluid reservoir.

In one exemplary aspect, the present disclosure is directed to a method of operating the landing gear of a trailer, the landing gear having a first and second jacks, each with a first tubular body in which a second tubular body is telescopically mounted, a hydraulic chamber and a pneumatic chamber. The method includes the steps of providing a pneumatic manifold having a plurality of internal passages defined therein; providing a hydraulic manifold having a plurality of internal passages defined therein; providing a single central control mechanism disposed to control pneumatic fluid flow through the pneumatic manifold; moving the central control mechanism to a first position, thereby causing hydraulic fluid to flow from a central hydraulic reservoir through the hydraulic manifold to the hydraulic chambers of the two jacks under a pneumatic head pressure generated within hydraulic reservoir from the pneumatic manifold; continuing to maintain the central control mechanism in the first position to activate hydraulic pumps so as to pump hydraulic fluid from the central hydraulic reservoir through the hydraulic manifold to the hydraulic chambers of the two jacks, thereby telescopically extending the second tubular body of each jack from the first tubular body of each jack; allowing the central control mechanism to self-center to a second position whereby pneumatic flow through the pneumatic manifold is inhibited; moving the central control mechanism to a third position thereby causing hydraulic fluid to flow from the hydraulic chambers of the two jacks, through the hydraulic manifold to the central hydraulic reservoir; and continuing to maintain the central control mechanism in the third position to supply pneumatic fluid flow from the a central pneumatic supply source through the pneumatic manifold to the pneumatic chambers of the two jacks, thereby retracting the second tubular body of each jack within the first tubular body of each jack. The method may further include the steps of providing first and second valves within the hydraulic manifold to control hydraulic fluid flow through the manifold back into the hydraulic reservoir; and actuating one or the other of the first and second valves in order to adjust the relative positions of the second tubular bodies.

In one exemplary aspect, the present disclosure is directed to a telescoping extension system having a first telescoping mechanism including a first telescoping mechanism with a first member slidingly disposed relative to a second member, a hydraulic chamber adjacent the sliding member and a pneumatic chamber adjacent the sliding member; a second telescoping mechanism having a first member slidingly disposed relative to a second member, a hydraulic chamber adjacent the sliding member and a pneumatic chamber adjacent the sliding member; a hydraulic fluid reservoir; a pneumatic fluid source; a pneumatic manifold in pneumatic fluid communication with the pneumatic source and in pneumatic fluid communication with said hydraulic reservoir; a hydraulic manifold in hydraulic fluid communication with the hydraulic reservoir; a first pneumatically operated hydraulic pump in pneumatic fluid communication with the pneumatic manifold and in hydraulic fluid communication with the hydraulic manifold; a second pneumatically operated hydraulic pump in pneumatic fluid communication with the pneumatic manifold and in hydraulic fluid communication with the hydraulic manifold; a central control mechanism attached to the pneumatic manifold and disposed to control pneumatic flow into the pneumatic chambers of the first and second telescoping mechanisms, the first and second pneumatically operated hydraulic pump and the hydraulic reservoir; and a first pneumatically operated hydraulic valve, separate from the central control mechanism, said first pneumatically operated hydraulic valve disposed to control hydraulic fluid flow from the hydraulic chamber of the first telescoping mechanism back into the hydraulic fluid reservoir.

The foregoing eliminates many of the leak points of the prior art systems, and also diminishes the likelihood of damage to the system from the operating environment or vibrations from operation of the tractor trailer. The system requires only a single hydraulic manifold and a single pneumatic manifold, thereby simplifying manufacture and maintenance of the system. In addition, by removing control mechanism and oil reservoir from the legs themselves, such a system will more readily permit the system to be retrofitted on existing trailers.

Although various embodiments and methodologies have been shown and described, the invention is not limited to such embodiments and methodologies and will be understood to include all modifications and variations as would be apparent to one skilled in the art. Therefore, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.