LEG CONTAINED LANDING GEAR ASSEMBLY

This patent application claims the benefit of the U.S. provisional patent application number 60/773,283, which was filed on February 13, 2006.

Background of the Invention (1) Field of the Invention

This invention pertains to a landing gear assembly 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 gearing transmission of a landing gear assembly 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 assembly is often used to support the trailer at the trailer forward end, maintaining a generally horizontal positioning of the trailer.

The typical landing gear assembly is attached to the underside of the trailer adjacent the truck coupling at the forward end of the trailer. The assembly 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 pulled outwardly 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 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.

Summary of the Invention

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 is entirely contained in a leg housing of the landing gear assembly. This enables the landing gear assembly of the present invention 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.

Conventional actuator screw and nut assemblies are provided inside the leg housings. Each actuator includes an input screw 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 screw 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 screw and nut 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 also includes an idler shaft that is mounted between the opposite side walls of the leg housing. In the preferred embodiment, the idler shaft is secured stationary relative to the leg housing, thereby reducing manufacturing costs of the landing gear assembly. A

plurality of idler gears are mounted for rotation on the idler shaft. In the preferred embodiment, the plurality of idler gears includes three idler gears that are all interconnected for rotation together. The three idler gears include a first idler gear that meshes directly with the first input gear, a second idler gear that meshes directly with the second input gear, and a third idler gear that meshes directly with an output gear mounted on the output shaft.

The output gear is a double gear combining a spur gear with a bevel gear. The spur gear is driven by the third idler gear, and the bevel gear drives the screw input gear of the actuator screw and nut assembly. In the compact construction of the gear mechanism of the invention, the output shaft is provided with a hollow interior bore at the end of the shaft in the master leg housing. The input shaft is provided with a reduced diameter portion on the end of the input shaft in the master leg housing. The reduced diameter portion of the input shaft is received in the interior bore of the output shaft for relative rotation and axial movement between the two shafts. In this manner, the connection of the output shaft to the leg housing actually provides support to the end of the input shaft mounted in the leg housing.

The novel gear mechanism of the invention provides a landing gear assembly with a two-speed operation where the gear mechanism is entirely contained in the landing gear assembly leg housing, removing the need for a separate casing or housing for the gear mechanism.

Brief Description of the Drawings

Additional features of the invention are set forth in the following detailed description of the preferred embodiment of the invention, and in the below listed drawing figures of the application wherein:

Figure 1 is a front perspective view of a pair of landing gear assembly legs that have been prepared for a conventional mounting to the front of a trailer, the legs being viewed from the perspective at the front of the trailer;

Figure 2 is a sectioned front elevation view of the landing gear assembly legs of Figure 1 ;

Figure 3 is a partial front elevation view, in section, of the gear transmission of the invention contained in the master leg housing shown on the right in Figure 2;

Figure 4 is a partial front elevation view, in section, of the gear transmission contained in the slave leg housing shown on the left in Figure 2;

Figure 5 is a front perspective view of the gears of the transmission shown in Figure 3;

Figure 6 is a front perspective view of the gears of the transmission shown in Figure 3; and,

Figure 7 is a perspective view of the output shaft of the transmission shown in~Figure 3.

Detailed Description of the Preferred Embodiment

Figure 1 shows a pair of landing gear assembly legs removed from a trailer. The legs are shown prepared for attachment by the conventional mount method to the trailer. Each of the legs is contained in a leg enclosure

or housing 12, 14. Each leg has a column 16, 18 that is received in a bottom opening of the respective leg housing 12, 14 for telescoping, vertical movement. An input shaft 22 enters the leg housing 12 commonly referred to as the master leg housing. The input shaft 22 is typically connected to a hand

crank that is manually rotated to selectively raise and lower the leg columns 16, 18 into and out of the respective leg housings 12, 14. An output shaft 24 extends out of the master leg housing 12 on an opposite side of the housing from the input shaft 22. The input shaft 22 and output shaft 24 are axially aligned. A second input shaft 26 extends into the leg housing 14 commonly referred to as the slave leg housing. A cross bar or cross tube (not shown) typically connects the master leg output shaft 24 to the slave leg input shaft 26 for rotation of the slave leg input shaft with the master leg output shaft. Thus, manual rotation of the master leg input shaft 22 by the hand crank selectively extends the leg columns 16, 18 from their respective leg housings 12, 14 to raise the trailer, or retracts the leg columns 16, 18 into their respective leg housings 12, 14 to lower the trailer.

Figure 2 shows a cross-section view of the master leg gear transmission and slave leg gear transmission of the present invention. The gear transmissions of the invention are designed to provide two gear ratios for adjusting the rates at which the leg columns 16, 18 are extended and retracted relative to their respective leg housings 12, 14. One novel feature of the invention is that the particular gearing configurations of the gear transmission of the invention enable all of the gears of the transmission to be contained inside opposing side walls of the leg housings 12, 14 of the landing

gear assembly. Each of the leg housings 12, 14 and their respective leg columns 16, 18 contain a conventional vertical screw 28 and nut 32 actuator assembly. Rotation of the screw 28 in the nut 32 of each assembly causes the reciprocating movement of the leg columns 16, 18 in their respective leg housings 12, 14. Each of the screw and nut assemblies has a screw input gear 34 at the top of the vertical screw. The bevel gear 34 in the preferred embodiment has twenty-two teeth, although the gear could have a different number of teeth. Rotation of the bevel gear 34 in opposite directions about a center axis 34a of the gear causes the reciprocating movement of the leg columns 16, 18 in their respective leg housings 12, 14.

Figure 3 is a front elevation view of the gear transmission of the invention contained in the master leg housing 12 of Figure 2.

The input shaft 22 is mounted on one side wall of the leg housing and extends entirely through the leg housing 12 of the master leg. The input shaft has a center axis of rotation 22a and a reduced diameter distal end 36 that fits into a complementary dimensioned socket 38 in the interior of the master leg output shaft 24. Thus, the input shaft 22 and output shaft 24 are coaxial, and the input shaft 22 can rotate relative to the output shaft 24. Furthermore, the output shaft socket 38 has a longer axial length than the reduced diameter

portion of the input shaft distal end 36. This allows the input shaft distal end 36 to move axially into and out of the output shaft socket 38 in shifting gear ratios of the transmission, as will be explained.

A key or shear pin 42 is mounted in a transverse bore through the input shaft inside the leg housing 12. The shear pin 42 functions as a key that

selectively secures input gears to the input shaft 22 by moving the input shaft axially between first and second positions relative to the leg housing 12.

A first, high speed input gear 44 and a second, low speed input gear 46 are mounted independently on the input shaft 22 in the leg housing 12. Both input gears 44, 46 are mounted for free rotation on the input shaft 22. The first input gear 44 has thirty-four teeth, and the second input gear 46 has twelve teeth. In alternate embodiments, the number of teeth on the input gears can change. The first input gear 44 has two pairs of diametrically opposed slots 48 formed in an end face of the input gear that opposes the second input gear 46. Only one pair of slots 48 is shown in Figure 3. The second pair of slots that is not visible in Figure 3 is rotated on the end face of the first input gear 44 ninety degrees from the first pair of slots 48. Each of the two pairs of slots 48 are dimensioned to receive the opposite ends of the key or shear pin 42 in the slots. Engagement of the shear pin 42 in the first input gear slots 48 secures the first input gear 44 to the input shaft 42 for rotation of the first input gear 44 with rotation of the input shaft 22.

The second input gear 46 also has two pairs of diametrically opposed slots 52 formed in the end face of the gear that opposes the first input gear 44. The second input gear slots 52 have the same configuration as the first input gear slots 48 and are mirror images of the first input gear slots. Like the first input gear slots 48, the second input gear slots 52 are dimensioned to receive the opposite ends of the shear pin 42 in the slots on axial movement of the input shaft 22 and the shear pin 42 to the left as shown in Figure 3. Engagement of the shear pin 42 in the second input gear slots 52 connects

the second input gear 46 to the input shaft 22 for rotation of the second input gear 46 with the rotation of the input shaft 22. Thus, with the input shaft 22 in a first position relative to the leg housing 12 shown in Figure 3, the shear pin 42 couples the first input gear 44 to the input shaft 22 for rotation of the input gear 44 with the input shaft 22, while the second input gear 46 is free to rotate on the input shaft 22. Movement of the input shaft 22 axially to its second position relative to the leg housing 12 moves the shear pin 42 into the slots 52 of the second input gear 46. This couples the second input gear 46 to the input shaft 22 for rotation of the second input gear 46 with the input shaft 22, while the first input gear 44 is free to rotate on the input shaft 22.

The transmission assembly also includes an idler shaft 54 with a center axis 54a secured in the leg housing 12. In the preferred embodiment, the idler shaft 54 is a step bolt that is secured by a self-locking nut 56 stationary inside the leg housing 12. An idler gear is mounted for free rotation on the idler shaft 54. In the preferred embodiment the idler gear is actually three gears, comprised of a high speed idler gear 58 that meshes with the high speed input gear 44, a low speed idler gear 62 that meshes with the low speed input gear 46, and an output idler gear 64. In the embodiment of the transmission shown in Figure 3, the high speed idler gear 58 has twelve teeth, the low speed idler gear 62 has thirty-four teeth, and the output idler gear 64 has eleven teeth. All of the three idler gears 58, 62, 64 are formed together as one gear assembly that is mounted for free rotation on the idler shaft 54. It can be seen in Figure 3 that the high speed idler gear 58 is in constant mesh with the high speed input

gear 44, and the low speed idler gear 62 is in constant mesh with the low speed input gear 46 as the input shaft 22 is moved axially between its first and second positions relative to the leg housing 12.

A double output gear that is comprised of an output spur gear 66 and an output bevel gear 68 is mounted on the output shaft 24. The output spur gear 66 is in constant mesh with the idler output gear 64, and the output bevel gear 68 is in constant mesh with the bevel input gear 34 of the screw and nut vertical actuator of the leg housing. In the preferred embodiment of the invention shown, the output spur gear 66 has thirty-five teeth and the output bevel gear 68 has fourteen teeth. The output spur and bevel gears 66, 68 are mounted on the output shaft 24 by a center bore 72 of the gear that has a general octagonal configuration. The eight-sided configuration of the gear

bore hole 72 can best be seen in Figures 5 and 6.

The end of the transmission output shaft 24 is provided with a complementary eight-sided exterior surface 74 shown in Figure 7. The engagement of the output shaft eight-sided surface 74 in the output gear bore hole 72 secures the output spur gear 66 and the output bevel gear 68 to the output shaft 24 for rotation with the shaft. The eight-sided surface 74 of the transmission output shaft 24 also produces four radially extending shoulder surfaces 76 on the output shaft. As seen in Figure 3, one side of the output spur gear 66 and output bevel gear 68 engages against the four radial shoulders 76 on the output shaft 24, preventing movement of the output spur gear 66 and output bevel gear 68 axially to the left relative to the output shaft 24 as viewed in Figure 3. A retaining ring 78 is inserted into a circular groove

82 formed in the output shaft 24 on the opposite side of the output spur gear 66 and output bevel gear 68. The engagement of the ring 78 in the groove 82 prevents the axial movement of the output spur gear 66 and the output bevel gear 68 to the left on the output shaft 24. In this way, the output spur gear 66 and output bevel gear 68 are mounted to the output shaft 24 around the portion of the shaft containing the shaft socket 38 without requiring a key way in the exterior surface of the output shaft that could significantly decrease the strength of the output shaft in the area of the socket 38.

The master leg output shaft 24 extends outwardly from the leg housing 12 of the master leg and is coupled by a cross bar (not shown) to the input

shaft 26 of the slave leg shown in Figure 4. The input shaft 26 of the slave leg extends entirely through the leg housing 14 and is mounted for rotation in the leg housing by a pair of bushings 84. A bevel output gear 86 is mounted on the input shaft 26 by a shear pin 88 that extends through the bevel gear 86 and the input shaft 26. In the preferred embodiment, the bevel gear 86 has fourteen teeth, the same number of teeth as the output bevel gear 68 of the master leg transmission. The output bevel gear 86 meshes with the bevel gear 34 of the screw 28 and nut 32 vertical actuator of the slave leg housing 14. The bevel input gear 34 of the actuator has the same number, i.e. twenty- two teeth, as the bevel input gear 34 of the screw 24 and nut 32 vertical actuator contained in the master leg housing 12.

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 Figure 3, rotation of the input shaft 22 by a manual crank causes rotation of

the first, high speed input gear 44. The constant mesh of the high speed input gear 44 with the high speed idler gear 58 causes the high speed idler gear to rotate together with the low speed idler gear 62 and the idler output gear 64. The low speed idler gear 62 is in constant mesh with the low speed input gear

46, and the rotation of the low speed idler gear 62 causes the low speed input gear 46 to rotate freely on the input shaft 22. The rotation of the idler output gear 64 is transferred to rotation of both the output spur gear 66 and the output bevel gear 68. Rotation of the output bevel gear 68 causes the bevel input gear 34 of the screw 28 and nut 32 linear actuator to rotate. This causes the vertical reciprocating movement of the leg column 16 in the leg housing 12. In addition, the rotation of the output spur gear 66 and output bevel gear 68 is transferred through the output shaft 24 of the master leg housing 12 to the input shaft 26 of the slave leg housing 14. The rotation of the input shaft 26 of the slave leg housing is transferred by the bevel gear 86 on the input shaft 26 to the bevel input gear 34 of the screw 28 and nut 32 linear actuator in the slave leg housing 14. This causes the vertical reciprocating movement of the leg column 18 in the leg housing 14.

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 pushed inwardly, causing the shear pin 42 to move out of the slots 48 of the first input gear, and into the slots 52 of the second input gear 46. This couples the second, low speed input gear 46 to

the input shaft 22 for rotation with the input shaft. The rotation of the low speed input gear 46 is transferred through the low speed idler gear 62 to the idler output gear 64. Rotation of the idler output gear 64 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 low speed input gear 46 has fewer teeth than the high speed input gear 44, 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. 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 28 and nut 34

vertical actuator for the leg. As seen in Figure 3, all of the gearing of the transmission is contained in the leg housing 12 positioned directly above the screw 28 and nut 34 vertical actuator. All of the shaft center axes 22a, 34a, 54a are positioned in the same plane. This provides the landing gear assembly of the invention with a more compact construction than prior art landing gear assemblies which required a separate gear box on the exterior of the leg housing, or a separate bolt-on shaft support housing on the exterior of the leg housing. Thus, the gear transmission of the present invention provides a constant mesh design of a two-speed landing gear transmission that does not require a separate gear box or separate shaft housing, and is contained in the same leg housing as the screw and nut vertical actuator of

the landing gear assembly leg.

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.