Abstract:
A mechanical jack that is used with trailers that has a functional combination of several working gears as well as a drop leg feature is disclosed. The mechanical jack has a gearbox having gears that not only have the capacity to handle a relatively heavy load, but also have the ability to handle small and midsize loads while maintaining sufficient and commercially acceptable cranking speeds without excessive force required. The jack includes a crank or handle for use with the mechanical jack that assists in both effective raising and lowering of the jack, as well as efficient transition from one working gear to another. The jack may also utilize an electric motor as the source of input power to the jack.

Description:
RELATED APPLICATION  
       [0001]     This application is a continuation-in-part application claiming the benefit of priority from U.S. patent application Ser. No. 10/368,519 filed on Feb. 18, 2003. 
     
    
     FIELD AND BACKGROUND OF THE INVENTION  
       [0002]     This invention relates generally to a multi-speed drop leg mechanical jack, and more particularly, to a multi-speed drop leg mechanical jack for use with a trailer.  
         [0003]     In the mechanical jack industry, and specifically where mechanical jacks are used with trailers, there is a continuing need to have user-friendly jacks that provide a commercially valuable balance of jack speed, lifting and lowering capabilities, ease of cranking and overall performance for both loaded and unloaded trailers. In mechanical jacks these variables are best overcome by selecting the appropriate gears by which the mechanical jack will operate, as well as anticipating the type of trailer that will be used with the jack.  
         [0004]     In many instances, it is desirable for mechanical jacks to have multiple gear ratios that not only have the capacity to handle relatively heavy loads, but also have the ability to handle small and midsize loads while maintaining sufficient and commercially acceptable cranking speeds without excessive force required.  
         [0005]     In addition, it is oftentimes desirable to be able to quickly provide elongation of the mechanical jack, such as in a drop leg, where there is not any mechanical cranking required in order to have a significant amount of jack elongation or contraction in a short amount of time, such as at the beginning or completion of the lifting process.  
         [0006]     Moreover, it is also desirable to provide an efficient way to change from one operating gear of the jack to another. To the extent that the operator of the jack can better use the crank of the jack to facilitate faster and smoother changes of operating gears, the crank will be considered to be advantageous. It is a continuing design goal to have a crank that facilitates operator use of the mechanical jack to which it is connected, in order to provide improved cranking and improved changing from one operating gear to another.  
         [0007]     Therefore, it would be advantageous to have a mechanical jack typically used with trailers that has a functional combination of several working gears as well as a drop leg feature. It would be particularly desirable if the drop leg feature was considered when selecting the working gears of the jack. It would also be advantageous to have a crank or handle for use with a mechanical jack that assists in both effective raising and lowering of the jack, as well as efficient transition from one working gear to another.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     Disclosed herein is a multi-speed drop leg mechanical jack for use with a trailer. The jack generally comprises at least two working gears and a drop leg. More particularly, the jack comprises an outer tubular housing; a inner tubular housing in mechanical engagement with the outer tubular housing, a drop leg in non-geared sliding engagement with the inner tubular housing; a gearbox mounted to the outer tubular housing, the gearbox comprising: a gear housing having an inner surface defined by gear housing teeth; a plurality of planet gears, each of the plurality of planet gears having teeth, the teeth in meshing engagement with the gear housing teeth; a planetary carrier connected to the plurality of planet gears, the carrier having an inner surface defined by planetary carrier teeth; and a sun gear having sun gear teeth, the sun gear axially slideable between a working high gear in which the sun gear teeth are in meshing engagement with the planetary carrier teeth and a working low gear in which the sun gear teeth are in meshing engagement with the teeth of the plurality of planetary gears.  
         [0009]     In another embodiment, a gearbox for use as part of a multi-speed drop leg mechanical jack for use with a trailer is disclosed. The gearbox comprises: a gear housing having an inner surface defined by gear housing teeth; a plurality of planet gears, each of the plurality of planet gears having teeth, the teeth in meshing engagement with the gear housing teeth; a planetary carrier connected to the plurality of planet gears, the carrier having an inner surface defined by planetary carrier teeth; and a sun gear having sun gear teeth, the sun gear axially slideable between a working high gear in which the sun gear teeth are in meshing engagement with the planetary carrier teeth and a working low gear in which the sun gear teeth are in meshing engagement with the teeth of the plurality of planetary gears; wherein the working high gear and the working low gear each have a turns per inch (TPI) parameter and each of the TPI parameters are selected at least in part to complement the drop leg.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The drawings illustrate the best mode presently contemplated for carrying out the invention. In the drawings:  
         [0011]      FIG. 1  is a schematic illustration of a multi-speed drop leg mechanical jack having a gearbox in accordance with one aspect of the present invention;  
         [0012]      FIG. 1   a  is an exploded perspective view of the multi-speed jack gearbox;  
         [0013]      FIG. 2  is a partial enlarged view of a handle for use with the multi-speed jack;  
         [0014]      FIG. 3  is a side sectional view of a portion of the multi-speed jack showing the jack in a working high gear position;  
         [0015]      FIG. 4  is a sectional view of a gearbox of the multi-speed jack taken along line  4 - 4  of FIG.  
         [0016]      FIG. 5  is a side sectional view of a portion of the multi-speed jack showing the jack in a working low gear position;  
         [0017]      FIG. 6  is a sectional view of a gearbox of the multi-speed jack taken along line  6 - 6  of  FIG. 5 ;  
         [0018]      FIG. 7  is a sectional view of the gearbox taken along line  7 - 7  of  FIG. 5 ; and  
         [0019]      FIG. 8  is a sectional view of a portion of the multi-speed jack taken along line  8 - 8  of  FIG. 5 .  
         [0020]      FIG. 9  is a perspective view of an alternate embodiment of the present invention utilizing a motor to provide input power to the jack, where the jack is engaged by the motor in high gear.  
         [0021]      FIG. 10  is a perspective view of the jack of  FIG. 9  where the jack is engaged by the motor in low gear.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     Referring to  FIG. 1 , a schematic illustration of a multi-speed drop leg mechanical jack  10  having a gearbox  12  in accordance with one aspect of the present invention is shown. The jack  10  can be used with a trailer  14 , partially shown  FIG. 1 . Trailers that are contemplated for use with the present invention include, but are not limited to, horse trailers, livestock trailers, large flatbed trailers, and construction equipment trailers.  
         [0023]     The jack  10 , in the embodiment shown, is generally a multi-speed mechanical jack incorporating a drop leg or “through the air” speed, and two geared working speeds, namely a working low gear speed that facilitates lifting of relatively higher loads, and a working high gear speed for faster lifting of relatively lower and medium-sized loads or lowering relatively high loads. As shown, gearbox  12  is connected, preferably so as to be flush mounted, to tubular housing  16  of jack  10 . Alternatively, gearbox  12  may be mounted within tubular housing  16  so as to have an internal gearbox arrangement. Tubular housing  16  can generally be referred to as a “concentric” tubular style, and in a preferred embodiment, a concentric, triple tubular style housing can be used. Tubular housing includes telescoping tubular sections  18   a  and  18   b.  Jack  10  further includes drop leg  20 . Drop leg  20  is in sliding, telescoping relationship tubular section  18   b.  Telescoping tubular sections  18   a,    18   b  and  20  are supported by jack base  22 . Tubular section  18   b  includes pin assembly  24  having pin  26 . Pin  26  is used to fix drop leg  20  in position relative to tubular section  18   b.  Gearbox  12  is connected to shaft  28 . Rotation of shaft  28  translates into linear movement of jack  10 , and more particular, tubular section  18   b  relative to tubular section  18   a,  in order to raise and lower trailer  14 . In one embodiment, jack  10  is fixedly connected to trailer  14 , for example, via mounting tabs  27  (schematically shown in phantom) which can be secured to trailer channel  29  in a known fashion. The drop leg is used to move quickly between a retracted position and an extended position in which the jack base is in close proximity to the ground. The drop leg movement helps provide the necessary clearance for the trailer, to which the jack is attached.  
         [0024]     Still referring to  FIG. 1 , crank  30 , also termed a leveraging actuator (e.g., a handle), is used to impart rotation as well as translation to the shaft. Crank  30  includes two grips or handles  32 ,  34 , which are separated by a contoured crank bar  36 . The grips are used to facilitate the imparting of a balanced translational and/or rotation force (i.e., torque) to shaft  28  as needed. Contoured crank bar  36  is shown in a preferred “L”-type configuration, however, any suitable shape or contoured configurations are contemplated. For example, contoured crank bar  36  can be bent or otherwise shaped to facilitate an end user&#39;s use of crank  30 .  
         [0025]      FIG. 1   a  is an exploded perspective view of multi-speed jack gearbox  12 . Gearbox  12  provides for the necessary engagement of the gears so as to impart motion of the shaft in two geared positions. Planetary carrier  38  carries planet gears  39   a - d,  having teeth  40   a - d  respectively, via connecting pins  42   a - d,  carrier  38 , planet gears  39   a - d  and connecting pins  42   a - d  are positioned within gear housing  46 , and more particularly, positioned such that teeth  40   a - d  are in meshing engagement with interior teeth  48  of the housing. Shaft  28  connects to planetary carrier  38  via pin  44 . Sun gear  50  includes teeth  52  and, via the teeth, meshingly engages either teeth  440   a - d  of planet gears  39   a - d,  or alternatively, interior teeth  54  of planetary carrier  38 , with these meshing engagements defining the two geared positions of gearbox  12 . Rotation of sun gear  50  via crank  50  ( FIGS. 1 and 2 ) imparts rotation and force transfer to shaft  28 . Gearbox  12  further includes input bushing  56  and output bushing  58  and is enclosed by endplates or cover portions  60   a - b.  Securing means  62  (e.g., a carriage bolt) and  64  are to fasten (typically from inside) the  10  gearbox together.  
         [0026]     Referring to  FIGS. 1-2 , in a preferred embodiment, crank  30  is removable, as indicated by the phantom illustration ( FIG. 1 ). Crank  30  includes connecting portion  65 , which extends from crank bar  36 , and slideably engages hollow sun gear shaft portion  28   a.  Pin  68  is secured to crank bar  36 , and more particularly, to slideable crank bar portion  70 . Both torque and translation forces are transmitted via pin  68  and holes  72   a  and  72   b  in connecting portion  65  and shaft portion  28   a  respectively. When it is desired to remove crank  30  from shaft  28 , for example, during transport of trailer  14  ( FIG. 1 ), the following is performed: a) raising slideable crank bar portion  70  of crank  30  in a direction indicated by arrow  66 , which in turn raises pin  68  by clearing the pin from holes  72   a  and  72   b,  respectively; and b) sliding connecting portion  65  out of shaft portion  28   a,  or sungear  50 , in a direction indicated by arrow  74  (i.e., axially along the shaft), thereby disengaging crank  30  from shaft  28  or sungear  50 . To engage the crank with the shaft, the above procedure is reversed. In one embodiment, the jack includes a connecting device to connect the crank to the shaft or may be connected directly to sungear  50 . The connecting device may include a spring-loaded detent (not shown) or other type of catch mechanism to secure the connecting device into position. In operation, when pin  68  is engaged, the detent emerges to lock or prevent movement of slideable crank bar portion  70 , and the detent retreats inside slideable crank bar portion  70  when pin  68  is disengaged to permit movement of the slideable crank bar portion.  
         [0027]     Turning to  FIGS. 3-4 , a side sectional view of a portion of the multi-speed jack showing the jack in a working high gear position, and a sectional view of a gearbox of the multi-speed jack taken along line  4 - 4  of  FIG. 3  are shown, respectively. In the working high gear position, sun gear teeth  52  of sun gear  50  are in meshing engagement with planetary carrier teeth  54  of planetary carrier  38 . Planetary carrier teeth  54  are formed to match the sun gear tooth form. In the working high gear position, sun gear  50  and planetary carrier  38  are disposed within gear housing  46 . Sun gear  50  is driven by crank  30  to rotate, for example in a direction indicated by arrow  76 , to drive planetary carrier  38 , for example in a direction indicated by arrow  78 . Planetary carrier  38 , in turn, causes rotation of shaft  28 , for example, in a direction indicated by arrow  80 .  
         [0028]     Turning to  FIGS. 5-6 , a side sectional view of a portion of the multi-speed jack showing the jack in a working low gear position, and a sectional view of a gearbox of the multi-speed jack taken along line  6 - 6  of  FIG. 5  are shown, respectively. In the working low gear position, sun gear teeth  52  of sun gear  50  are in meshing engagement with planet gear teeth  40   a - d  of planet gears  39   a - d.  In the working low gear position, sun gear  50 , planetary gears  39   a - d,  and planetary carrier  38  are disposed within gear housing  46 . Sun gear  50  is again driven by crank  30  to rotate, for example in a direction indicated by arrow  88 , and drive planet gears  39   a - d,  for example in a direction indicated by arrow  90 . In addition, planet gear teeth  40   a - d  of planet gears  39   a - d  meshingly engage housing interior teeth  48  of housing  46 , and thus, as planet gears  39   a - d  rotate in the direction indicated by arrow  90 , the planet gears also revolve in a direction indicated by arrow  92 . Planet gears  39   a - d  are connected, for example via pin  94  as shown, to planetary carrier  38 . Thus, as planet gears  39   a - d  rotate and revolve, planetary carrier  38  is itself carried in the direction indicated by arrow  92 . Planetary carrier  38  causes rotation of shaft  28 , for example, in a direction indicated by arrow  80 . It is noted that this gearing arrangement rotates shaft  28  in the same direction as crank  30  in both geared positions. Such an arrangement may tend to decrease novice operator confusion and directional errors when switching gears.  
         [0029]     As shown in  FIGS. 3 and 5 , crank  30  is used to shift between the working high gear position and the working low gear position. More particularly, a jack user can push or pull on crank  30  to move the crank in directions indicated by arrows  96  and  98 . Since crank  30  is connected, for example via pin  68  ( FIG. 2 ) to shaft  28  or sun gear  50 , the sun gear axially slides between the working high gear position ( FIG. 4 ), in which sun gear teeth  52  are in meshing engagement with planetary carrier teeth  54  and the working low gear position ( FIG. 6 ), in which the sun gear teeth are in meshing engagement with planet gear teeth  40   a - d  of planet gears  39   a - d.  As will be further described below, other types of actuators can be used, including a motor that can be shifted between high gear and low gear to operate the jack without user cranking.  
         [0030]     Turning to  FIG. 1 , crank  30  can be termed a “low friction” crank in that it minimizes frictional losses when shifting between the working high gear position and the working low gear position by providing, via handles  32 ,  34 , balanced exertion forces on shaft  28 .  
         [0031]      FIG. 7  is a sectional view of the gearbox taken along line  7 - 7  of  FIG. 5 . As shown, connector  44 , for example a pin connector, connects planetary carrier  38  with shaft  28 . In the working low gear position shown, sun gear  50  (shown in phantom) causes, via planet gears  39   a - d,  rotation of carrier  38 , in turn rotating shaft  28 .  
         [0032]      FIG. 8  is a sectional view of a portion of the multi-speed jack taken along line  8 - 8  of  FIG. 5 . As shown, gear  82  is connected to shaft  28  and is in meshing engagement with crown gear  84 , with the crown gear in turn connected to jack shaft  86 . In a known manner, rotation of shaft  28  causes linear displacement of jack shaft  86 , via crown gear  84 , to raise and lower jack  10 .  
         [0033]     In the working high gear, preferably between about 7 turns and 11 turns, and more preferably about 9 turns, of sun gear  50  ( FIGS. 3-4 ) results in about one inch of linear displacement of jack shaft  86  ( FIGS. 3-4 ,  8 ), with this relationship generally referred to as “turns per inch” or TPI. In one preferred embodiment, the working high gear raises loads that range from about 2,500 lbs to about 4,500 lbs and lowers loads that range from about 4,200 lbs to about 7,500 lbs. In the working high gear, one (1) revolution of sun gear  50  results in one (1) revolution of planetary carrier  38  ( FIGS. 3-4 ).  
         [0034]     The working low gear, preferably results in between about 24 and 30, and more preferably about 27.75 TPI. In one preferred embodiment, the working low gear raises loads that range from about 4,500 lbs to about 10,000 lbs and lowers loads from about 7,500 lbs and above. In the working low gear position, three (3) revolutions of sun gear  50  results in one (1) revolution of planetary carrier  38  ( FIGS. 5-6 ).  
         [0035]     Accordingly, the ratio of the working low gear to the working high gear, termed the “working low gear-to-working high gear ratio” is preferably between about 2.4 to 1 and 5 to 1, more preferably about 3 to 1, and even more preferably about 3.1 to 1. In one preferred embodiment, the gear ratio is 3.0833 to 1.  
         [0036]     Typically the working low gear ratio (or mechanical advantage) is chosen based on a maximum lifting load. The working high gear ratio, in contrast, is chosen based on speed. In the present invention, both the working low gear and working high ratios are selected for use specifically with the jack drop leg feature. Because the drop leg provides the through-the-air function, the typical speed consideration becomes unimportant; therefore the working high gear ratio can be chosen based on raising or lowering significant but less than maximum loads. The user is therefore not confined to lift and lower all loads with only the working low gear, especially important when the size of the load is very small.  
         [0037]     The design of the gear ratios can take into account the fact that the drop leg is available, and as part of the design criterion, the working high gear and the gear ratios can be selected to carry a significant load. As a result, designing the working gears with the drop leg in mind eliminates high working gears that have to carry no load. Also, the gears can be operator selected to lift various loaded trailers with as much speed as possible. The overall efficiency is increased by reducing the time to raise and lower the jack in the loading conditions for which it is made. The two working gears plus drop leg design model is particularly desired when the loads change from fully loaded to unloaded, and where loading and unloading occurs frequently, such as in vehicle or animal trailers. The working high gear and the working low gear each have a turns per inch (TPI) parameter and each of the TPI parameters are selected at least in part to complement the drop leg. By “complement” it is mean that the TPI parameters are selected based on the anticipation of the availability of the drop leg.  
         [0038]     Another embodiment, as shown in  FIGS. 9 and 10 , utilizes an actuator comprising an electric motor to input power to the jack rather than a hand crank. The motor  100  eliminates the need for human effort to input power to the jack. Such an improvement retains the “shift ability” of the gearbox but does not require manual cranking. Other than the motorized actuator  100 , the construction of the jack is substantially identical that the previous embodiment.  
         [0039]     As shown in  FIG. 9 , a motor assembly  102  comprises a gear motor  100 , a motor gearbox  110 , and a sungear  112 . The motor  100  provides power through the motor gearbox  110  to supply torque to the sungear  112 . As shown in  FIG. 9 , the sungear  112  engages the planetary gear carrier  50  to provide input power in a high gear. Therefore, the operation of the jack performs as described above relative to power input at a high gear. As shown in  FIG. 10 , the motor assembly  100  can pulled outwardly so as to move the sungear  12  out of engagement with the planetary gear carrier  50  and into engagement with the planetary gears  39  so as to provide input power in a low gear. Therefore, the operation of the jack performs as described above relative to power input in a low gear. With regard to the selection of gear speed, it is anticipated that the shifting mechanism of the motor assembly could be done manually or automatically without further description herein.  
         [0040]     The present invention has been described with respect to several embodiments. Equivalents, alternatives, and modifications, aside from those expressly stated herein, are possible and should be understood to be within the scope of the appending claims.