Patent Application
20080315570
(1) Field of the Invention
This invention pertains to a landing gear apparatus that supports the front end of a trailer when the trailer is not being pulled by a truck. In particular, the present invention pertains to a landing gear apparatus having a gearing transmission of a simplified, reduced cost construction that is entirely contained inside the leg housing enclosing the landing gear assembly.
(2) Description of the Related Art
Many of the different types of trailers that are towed by trucks are connected to the trucks by a releasable coupling such as a gooseneck coupling or a fifth-wheel coupling. When the trailer is released from the truck and is no longer supported by the truck at the forward end of the trailer, a landing gear apparatus is often used to support the trailer at the trailer forward end, maintaining a generally horizontal positioning of the trailer.
The typical landing gear apparatus is attached to the underside of the trailer adjacent the truck coupling at the forward end of the trailer. The apparatus can have a single leg housing that is attached at a forward end of a trailer for example a goose neck trailer, but often includes a pair of vertically oriented leg housings positioned adjacent opposite sides of the trailer. A vertical leg column is mounted in each housing. A gear mechanism on each leg is selectively operated to lower the columns from the leg housings, or raise the columns on the leg housings. The gear mechanisms of the two leg housings are connected together by a shaft assembly that extends across the underside of the trailer between the two leg housings. A hand crank is connected to the shaft assembly at one side of the trailer. Selectively rotating the hand crank in opposite directions lowers the pair of leg columns until the columns contact the ground and support the trailer forward end when the trailer is being uncoupled from the truck, or raise the pair of columns when the trailer has been connected to a truck and is ready for towing.
Many prior art landing gear assemblies have two-speed gear mechanisms that enable the columns of the landing gear assembly to be lowered and raised at different speeds or at different rates. The input shaft of the landing gear assembly is moved axially inwardly and outwardly relative to the trailer to shift the assembly between the two speeds. For example, the landing gear assembly input shaft can be pushed inwardly by the truck operator to shift to a high speed gear. Rotation of the input shaft by the hand crank will then cause the columns of the landing gear assembly legs to be lowered or raised at a faster rate. This enables the leg columns of the landing gear assembly to be lowered quickly until they come into engagement with the ground beneath the trailer when it is desired to uncouple the trailer from the truck. The gear mechanism of the landing gear assembly is then shifted to a low gear ratio by pushing axially on the crank, moving the input shaft axially inwardly toward the trailer assembly. When shifted to the low gear ratio, more power is transferred to the leg columns by the reduction gearing of the landing gear assembly gear mechanism. For each rotation of the crank, the leg columns are lowered at a slower rate, but more power is transferred to the columns enabling the landing gear assembly to lift the trailer from the truck when uncoupling the trailer from the truck.
Prior art landing gear assemblies that include gear mechanisms that provide a high-speed, low-torque operation or a low-speed, high-torque operation typically include a separate casing or housing for the gear mechanism. The separate casing is needed to contain the many gears and clutching mechanisms typically employed in the prior art gear mechanisms. The gear mechanism housing is typically attached to a side of one of the leg housings of the landing gear assembly. In some prior art landing gear assemblies, gear mechanism housings are attached to the sides of both leg housings.
The positioning of the gear mechanism housings on the sides of the leg housings at times makes it difficult to attach a landing gear assembly to a particular construction of a truck trailer. The need to provide a separate gear mechanism housing in addition to the leg housing increases the costs involved in manufacturing the landing gear assembly. Furthermore, positioning of the gear mechanism housing relative to the leg housing may limit the landing gear assembly for attachment only to the outsides of frame members of the trailer, or to the insides of frame members of the trailer.
Furthermore, as stated earlier, the prior art gear mechanisms used on trailer landing gear assemblies typically included an elaborate arrangement of gears and clutches that enable the gear mechanism to shift between two speeds and two torques simply by axially moving the input shaft between two axially spaced positions. The increased numbers of gears, countershafts, and clutching mechanisms in the prior art gear mechanisms contribute to the overall cost of manufacturing the gear mechanisms. Thus, the greater number of gears, countershafts, and clutch mechanisms required by a gear mechanism, the greater the cost involved in manufacturing the gear mechanism.
The landing gear assembly of the present invention overcomes the above-discussed disadvantages of prior art landing gear assemblies by providing a landing gear assembly with a two-speed or two-torque gear mechanism that has a simplified, reduced cost construction and is entirely contained in a leg housing of the landing gear assembly. This enables the landing gear assembly of the present invention to be economically manufactured and to be readily used with various different types of trailer configurations.
The landing gear assembly is provided in a master leg and slave leg arrangement, where the power for lifting and lowering the truck trailer is provided by the master leg, as is conventional. An input shaft enters one side of the leg housing of the master leg and an output shaft exits the opposite side of the leg housing. The output shaft extends across the landing gear assembly to drive a bevel gear mechanism in the slave leg. The bevel gear mechanism extends and retracts the length of the slave leg to match the extension and retraction of the master leg. The novel gearing mechanism of the invention is comprised of only an input shaft and an output shaft, and does not require any other additional shafts for supporting gearing of the mechanism. Reducing the number of shafts required by the gearing mechanism reduces the cost of manufacturing the gearing mechanism.
Conventional actuator screw and nut assemblies are provided inside the leg housings. Each actuator includes an actuator input gear that drives a screw of the actuator that in turn extends the leg column from the leg housing and retracts the leg column into the leg housing, depending on the direction of rotation. The gear mechanism of the invention drives both the output shaft that is operatively connected to the slave leg and the actuator input gear at two different rates of rotation. The gear mechanism is shifted between the two different rates of rotation by manually moving the input shaft axially between first and second positions of the input shaft relative to the leg housing. The gear mechanism of the invention is entirely contained within the opposite side walls of the leg housing that contain the actuator assembly.
The gear mechanism of the invention includes a first, high-speed input gear and a second, low-speed input gear that are both mounted on the input shaft. The first and second input gears are mounted for independent rotation on the input shaft. The input shaft is provided with a key that engages the first input gear to the input shaft in the first position of the input shaft, and engages the second input gear to the input shaft in the second position of the input shaft. When the first input gear is engaged to the input shaft, the second input gear is free to rotate relative to the first input gear and the input shaft. When a second input gear is engaged to the input shaft, the first input gear is free to rotate relative to the second input gear and the input shaft.
The gear mechanism of the invention also includes an output gear that is secured stationary to the output shaft inside the leg housing, a first driven gear that is secured stationary to the output shaft inside the leg housing, and a second driven gear that is secured stationary to the output shaft inside the leg housing. In the preferred embodiment, the output gear, the first driven gear, and the second driven gear are all part of a one-piece gear element that is secured to the output shaft. This construction of the gear element further reduces the manufacturing cost of the landing gear apparatus. The output gear meshes directly with the actuator input gear. The first driven gear meshes directly with the first drive gear and has a fewer number of gear teeth than the first drive gear. Thus, each rotation of the first drive gear with the input shaft drives the first driven gear and the output shaft in more than one rotation. The second driven gear meshes directly with the second drive gear and has a greater number of gear teeth than the second drive gear. Thus, each rotation of the input shaft and the second drive gear rotates the second driven gear and the output shaft in less than one rotation. However, the second drive gear imparts more torque to the second driven gear than does the first drive gear to the first driven gear.
A clutch mechanism in the form of a shear pin secured to the input shaft selectively secures the first drive gear or the second drive gear to the input shaft for rotation with the input shaft. When the first drive gear is secured to the input shaft, the second drive gear rotates freely on the input shaft. When the second drive gear is secured to the input shaft, the first drive gear rotates freely on the input shaft.
Moving the input shaft axially inwardly into the leg housing secures the first drive gear to the input shaft. Rotation of the input shaft with the first drive gear secured to the input shaft drives the first driven gear on the output shaft in rotation and in turn causes the actuator assembly to lower and raise the leg column relative to the leg housing at a faster rate, depending on which direction the input shaft is turned by the manual crank connected to the input shaft. Pulling the input shaft axially outwardly secures the second drive gear to the input shaft. Rotating the input shaft with the second drive gear secured to the input shaft causes the second drive gear to drive the second driven gear on the output shaft, which in turn drives the actuator assembly to raise and lower the leg column relative to the leg housing at a slower rate, depending on the direction of rotation of the input shaft by the manual crank. The gearing ratio of the second drive gear and the second driven gear, although moving the leg column more slowly relative to the leg housing, imparts greater torque to the output shaft and the actuator assembly, and thereby makes it easier to lift the weight of the trailer.
If so desired, the landing gear apparatus can be used as a single lifting apparatus for a trailer, for example a goose neck trailer. The landing gear apparatus can also be connected to a second slave leg by connecting the output shaft of the apparatus to an input shaft of the second leg.
The novel gearing arrangement of the invention allows the landing gear apparatus to be constructed more compactly in a single leg housing, and more cost efficiently. The simplified gearing mechanism enables the input shaft, the output shaft, and a screw shaft of the actuator assembly to be positioned in a single plane, with these shafts being the only shafts contained in the leg housing. The reduced number of gears required by the gearing mechanism also reduces the cost of manufacturing the apparatus. Furthermore, the novel gear mechanism of the invention provides a landing gear apparatus with a two-speed operation where the gear mechanism is entirely contained in the landing gear assembly leg housing, removing the need for separate casing or housing for the gear mechanism.
Further features of the invention are set forth in the following detailed description of the preferred embodiment of the invention, and in the drawing figures.
Referring to
Referring to
The gear mechanism input shaft 22 has an interior portion 46 that is mounted in the interior volume 44 of the leg housing, and an exterior portion 48 that is positioned outside the leg housing interior volume in the exterior environment of the apparatus. The input shaft interior portion 46 is mounted by a pair of bushings 52 to the first sidewall 38 and second sidewall 42. The bushings 52 allow the input shaft 22 to rotate about a center axis 54 of the input shaft, and move axially along the center axis 54. The input shaft 22 is movable between first and second axially spaced positions relative to the leg housing 12.
A clutch mechanism in the form of a shear pin 58 is provided on the interior portion of the input shaft 46. The shear pin 58 is secured to the input shaft interior portion 46 and rotates and moves axially with the input shaft. The pin 58 is mounted in a transverse bore through the input shaft interior portion 46. The pin 58 functions as a key that selectively secures input gears to the input shaft by the axial movement of the input shaft between its first and second positions relative to the leg housing 12, as will be explained.
The output shaft 24 has an interior portion 62 that is also mounted between the first 38 and second 42 sidewalls of the leg housing 12 and an exterior portion 64. A pair of bushings 66 mount the output shaft 24 to the leg housing sidewalls 38, 42 for rotation of the output shaft relative to the leg housing. The output shaft 24 has a center axis 68 that is parallel to the input shaft center axis 54, but is spaced vertically from the input shaft axis. The output shaft 24 does not move axially relative to the leg housing 12 and is held against axial movement by the constructions of the particular bushings 66. The output shaft exterior portion 64 is provided with means for connecting the output shaft to the input shaft 26 of the second, separate landing gear apparatus, such as the slave leg shown to the left in
A gear element 72 is secured stationary on the output shaft 24 for rotation with the output shaft. The gear element 72 is shown secured to the output shaft 24 by a pin 74 inserted through the gear element and through the shaft. Other means of securing the gear element 72 to the output shaft 24 could be employed. The gear element 72 is comprised of three different gears that are formed as one monolithic piece on the gear element 72.
An output gear 76 is formed on the gear element 72. The output gear 76 is a bevel gear that meshes directly with the actuator input gear 34. In the preferred embodiment, the bevel output gear 76 has 20 teeth.
A first driven gear 78 is also formed on the gear element 72. The first driven gear 78 is a spur gear. In the preferred embodiment, the first driven gear 78 has 11 teeth.
A second driven gear 82 is also formed on the gear element 72. The second driven gear 82 is also a spur gear. In the preferred embodiment, the second driven gear 82 has 29 teeth. Each of the output gear 76, the first driven gear 78, and the second driven gear 82 are formed as one piece on the gear element 72 and are all secured stationary to the output shaft 24 inside the leg housing interior volume 44 for rotation of the gears with the output shaft.
A first drive gear 84 is mounted for rotation on the input shaft 22 inside the leg housing interior volume 44. The first drive gear 84 is a spur gear that meshes directly with the first driven gear 78 on the output shaft 24. In the preferred embodiment, the first drive gear 84 has 29 teeth. The first drive gear 84 is provided with one or more interior slots 86 in an end face of the gear. The slots 86 are dimensioned to receive the key clutch member 58 on the input shaft 22 when the input shaft is moved to its first position relative to the leg housing 12. This position of the clutch mechanism 58 is shown in
A second drive gear 88 is mounted on the input shaft 22 for rotation of the second drive gear relative to the input shaft. The second drive gear 88 is a spur gear that meshes directly with the second driven gear 82. In the preferred embodiment, the second drive gear 88 has 11 teeth. The second drive gear 88 is also provided with one or more slots 92 that extend axially into an end face of the gear. The slots 92 are in an end face of the second drive gear 88 that opposes the end face of the first drive gear 84 having the slots 86. The slots 92 in the second drive gear 88 are also dimensioned to receive the clutch mechanism pin 58 when the input shaft 22 is moved to its second axial position relative to the leg housing 12. Receipt of the clutch mechanism pin 58 in the second drive gear slot 92 secures the second drive gear 88 to the input shaft 22 for rotation of the gear with the shaft. When the input shaft 22 is moved to its first axial position relative to the leg housing 12, the clutch mechanism pin 58 is withdrawn out of the second drive gear slot 92 and the second drive gear 88 is free to rotate on the input shaft 22.
The second input shaft 26 of the second leg housing 14 is mounted by a pair of bushings 96 between a first sidewall 98 and a second sidewall 102 of the housing. The bushings 96 mount the second input shaft 26 for rotation in the second leg housing 14, and hold the input shaft against axial movement. The second input shaft 26 is operatively connected to the output shaft 24 by the cross bar 28. Thus, the second input shaft 26 rotates with the output shaft 24.
An additional drive gear 102 is secured to the second input shaft 26 for rotation with the second input shaft. The additional drive gear 102 is a bevel gear that meshes directly with the actuator input gear 34 in the second leg housing 14. The additional drive gear 102 has the same number of teeth as the output gear 76. Thus, rotation of the output shaft 24 causes the screw and nut actuator assemblies 32 in each of the leg housings 12, 14 to simultaneously move their respective leg columns 16, 18 between their retracted and extended positions relative to the leg housings, depending on the direction of rotation of the input shaft 22.
In operation of the gear transmission of the invention, with the input shaft 22 of the master leg housing 12 in the first, high speed position shown in
In the high speed position of the input shaft 22 described above, the vertical adjustments of the leg columns 16, 18 in their respective leg housing 12, 14 occur more quickly.
To shift the gear transmission to low speed operation, the input shaft 22 of the master leg housing 12 is pulled outwardly, causing the shear pin 58 to move out of the slots 86 of the first drive gear, and into the slots 92 of the second drive gear 88. This couples the second, low speed drive gear 88 to the input shaft 22 for rotation with the input shaft. The rotation of the low speed second drive gear 88 is transferred through the second driven gear 82 to the output gear 76. Rotation of the output gear 76 causes the vertical reciprocating movements of the leg columns 16, 18 in their respective leg housings 12, 14 in the same manner discussed above. However, because the second drive gear 88 has fewer teeth than the first drive gear 84, the vertical adjusting movements of the leg columns 16, 18 in their respective leg housings 12, 14 do not occur as quickly as when the transmission is operated in high speed, but greater torque is provided for lifting the trailer.
The novel design of the landing gear assembly gear transmission described above allows all of the gearing of the transmission to be contained in the same master leg housing 12 that contains the screw and nut vertical actuator for the leg. As seen in
Although only one embodiment of the landing gear assembly has been described above, it should be understood that other modifications and variations could be made to the landing gear assembly without departing from the scope of the invention defined by the following claims.
