Abstract:
A center motor driven stabilizer jack having a motor driven slip differential which drives a left and a right thread screw lowering attached stabilizer legs which adjust and compensate for uneven terrain at the same time. The stabilizer jack slip differential, motor and the thread screws are mounted horizontally providing a low profile. The center drive system creates a beam style support the stabilizer legs to be moved further out for greater stability.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to stabilizer jacks, and in particular, to motorized stabilizer jacks for recreational vehicles adapted to raise a recreational vehicle relative to its suspension to provide stability to the vehicle when parked. 
     It is desirable to stabilize recreational vehicles once the vehicle is parked for use. A wide variety of recreational vehicle stabilizing jacks have been developed for use in stabilizing recreational vehicles, trailers, and the like, when parked. Prior art jacks raise the vehicle relative to its suspension system thereby preventing rocking and swaying of the recreational vehicle as an occupant moves around in the vehicle. Early stabilizing jacks provided on recreational vehicles were manually operated, requiring the owner to walk around the vehicle and manually operate four jacks to stabilize the vehicle at a campsite. This operation may be difficult and cumbersome, especially at night or in adverse weather conditions. 
     Later prior art stabilizer jacks were motorized, but still had problems. The motors used were often prone to damage during transport of the recreational vehicle because of clearance problems. Other motorized jacks operated each leg independently making it difficult to properly stabilize the vehicle. U.S. Pat. No. 6,224,102 to Nebel discloses a motorized stabilizer jack utilizing a single drive screw with left and right hand threads with a drive unit mounted to the end of the screw drive. During terrain compensation of this device, the drive screw is forced to move left to right on the body of the recreational vehicle. Mounting the motor on the end of the drive screw creates one of two problems. In the first condition, if the motor is mounted inside the body of the recreational vehicle, the amount of screw available for use is limited, causing the stabilizer legs to be closer together under the vehicle. In a second alternative condition, the motor is mounted outside of the body of the recreational vehicle. When maneuvering in tight areas such as camp grounds, the motor can be damaged, as well as the vehicle itself, because of trees and rocks. U.S. Pat. No. 5,826,889 to Eden utilized a vertical screw drive that is rotated in position at the time of use. The space required to operate such a system is not always available under the recreational vehicle thereby limiting its functionality. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing disadvantages inherent in the known types of devices now present in the prior art, the present invention has as its main objective to provide a motorized stabilizer jack that has a low profile and fits under a recreational vehicle in a small area without protruding parts. A further objective is to provide a motorized stabilizer jack able to position the stabilizer to the furthest outside edge of the recreational vehicle body thereby providing enhanced stability. 
     To attain this, the present invention provides a motor driven slip differential which drives a left and a right thread screw lowering stabilizer legs which adjust and compensate for uneven terrain at the same time. The present invention slip differential system has torque balancing properties across two shafts. This allows complete terrain compensation through the entire stroke of the two stabilizers without the need for a balancing electric circuit. The present invention shafts and the drive screw are mounted horizontally making the present invention the only known low profile motor driven under chassis assembly. The present invention&#39;s center drive system creates a beam style support allowing the stabilizer legs to be moved further out for greater stability. 
     These together with other objects of the invention, along with various features of novelty which characterize the invention, are pointed out with particularity in the claims annexed hereto and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there is illustrated a preferred embodiment of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a recreational vehicle having a deployed stabilizing jack secured beneath the rear chassis. 
     FIG. 2 is a perspective front view of the motor driven differential. 
     FIG. 3 is a side perspective view of the motor driven differential. 
     FIG. 4 is a front perspective view of the invention 
     FIG. 5 is a is a front perspective view, partly in section, of one stabilizer leg. 
     FIG. 6 is a front view of the invention in a closed position. 
     FIG. 7 is a front view of the invention showing deployable positions of the stabilizer legs. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings in detail wherein like elements are indicated by like numerals, there is shown a recreational vehicle  1  with a stabilizer jack assembly  10  attached to a frame member  3 . The recreational vehicle  1  is shown parked on a pad  4  and overhanging the ground  5  around the pad  4 . The recreational vehicle  1  is supported on a spring suspension system (not shown) connected to wheels  2 . The suspension system is adapted to provide a smooth ride during travel. However, when the recreational vehicle  1  is parked, the suspension system allows the vehicle  1  to rock back and forth and bounce up and down relative to the wheels  2  as an occupant moves around the vehicle  1 . 
     The purpose of the stabilizer jack assembly  10  is to raise the vehicle  1  upward relative to the wheels  2  to take some of the weight of the vehicle  1  off of the suspension system to stabilize the vehicle  1  and prevent rocking and bouncing of the parked vehicle  1 . In the embodiment and recreation vehicle shown, one stabilizer jack assembly  10  is mounted across and under the rear end  6  the vehicle  1 , rearward of the wheels  2 , by attachment to a frame member  3  protruding downward from the vehicle body bottom  8 . In other types of recreational vehicles a second stabilizer jack assembly could be mounted across and under the front  7  of the vehicle. Although the pad  4  will be generally level, bare ground or ground  7  around a pad may not be level. 
     The stabilizer jack assembly  10  of the present invention is comprised of a motor drive slip differential assembly  11 , driving an elongated left  20  and an elongated right  21  thread screw lowering and raising attached stabilizer legs  30 . The stabilizer jack assembly  10  is further comprised of a guide rail  40  encompassing each thread screw  20 ,  21 . Each guide rail  40  is attached to a vehicle frame member  3  and supports the load from the vehicle  1 . 
     The differential assembly  11  which can most clearly be understood by viewing FIGS. 2 and 3, is comprised of a motor  12  with a drive shaft  13   a  driving a first gear  13   b . The first gear  13   b  engages a second gear  14  directly attached to a worm gear  15 . The worm gear  15  engages a toothed wheel  16 . The toothed wheel  16  is directly attached to a slip differential casing  25 . A first output shaft  17  and a second output shaft  19  are attached to miter gears (not shown) within a slip differential  18 . The shafts  17 ,  19 , slip differential  18 , and motor  12  lay generally in a horizontal plane generally parallel to the vehicle body bottom  8 . The motor  12  torque is translated to the output shafts  17 ,  19  via the gears  13   b ,  14 ,  15 , toothed wheel  16  and slip differential  18 . The slip differential  18  enables one output shaft to continue turning regardless of resistant encountered by the other shaft. The gears  13   b ,  14 ,  15 , toothed wheel  16 , differential  18  and output shafts  17 ,  19  are housed in a generally rectangular box  50 , with the output shafts  17 ,  19  protruding out of the box interior  54  through opposite box sides  51 . The motor  12  is attached to another box side  53  external to the box  50 . The motor drive shaft  13   a  protrudes from the motor  12  into the box interior  54 . 
     Each thread screw  20 ,  21  is housed within a guide rail  40 . Each guide rail  40  has a generally rectangular cross section, a top  41 , an open bottom  42 , a front  43 , a rear  44 , a proximal end  45  and a distal end  46 , said proximal end  45  and distal end  46  defining a guide rail longitudinal axis. The guide rail top  41 , bottom  42 , front  43 , rear  44 , proximal end  45  and distal end  46  define a guide rail interior  48 . The guide rail top  41  may have a longitudinal groove or channel  47  formed therein to strengthen the guide rail  40 . The guide rail proximal end  45  abuts a box shaft side  52  and accepts one of the output shafts through its proximal end  45  into its interior  48 . A bracket  56  is attached over the box  50  and proximal ends  45  of the guide rails  40 . The guide rail tops  41  are attached to vehicle frame members  3 . 
     The screws  20 ,  21  lay entirely within the interior  48  of their respective guide rail  40 . The left thread screw  20  is directly coupled to the second output shaft  19 . The right thread screw  21  is directly coupled to the first output shaft  17 . Each screw has an end  22  opposite to the one coupled to an output shaft  17 ,  19 . Each screw opposite end  22  is rotationally joined to a guide rail distal end  46 . 
     A generally rectangular positioning block  60  is threadingly engaged to each screw  20 ,  21  within the guide rail interior  48 . Each positioning block  60  has a top  61 , a bottom  62 , a front  63 , a rear  64 , a proximal end  65  and a distal end  66 , said proximal end  65  and distal end  66  defining a positioning block longitudinal axis, said positioning block longitudinal axis being coincident with the guide rail longitudinal axis. The positioning block  60  has an interior, threaded aperture  67  from the proximal end  65  to the distal end  66 . Each screw  20 ,  21  threadingly engages the interior aperture  67  of its respective positioning block  60 . The positioning block bottom  62  faces the guide rail open bottom  42 . 
     The stabilizer jack  10  has two stabilizer legs  30 , each comprised of an elongated support leg  31  and an elongated fixed linkage  35 . Each support leg  31  has an attachment end  32 , a support end  33 , and a body  34  interconnecting said ends  32 ,  33 . Each support leg attachment end  32  is pivotally connected to the bottom  62  of a positioning block  60 . Each support end  33  is adapted to rest on the ground  4  or  5 . Each fixed linkage  35  has two ends, a rail attachment end  36  and a support attachment end  37 . The fixed linkage rail attachment end  36  is pivotally joined at the guide rail bottom  42  to the guide rail distal end  46 . Each fixed linkage support attachment end  37  is pivotally attached to a respective support leg  31  at a point  38  intermediate of the support leg ends  32 ,  33 . 
     In operation, the motor  12  drives the slip differential assembly  11  causing the shafts  17 ,  19  and their respective drive screws  20 ,  21  to rotate. The screw rotation causes each positioning block  60  to move along its respective screw  20 ,  21 . The movement of a positioning block  60  forces its respective attached stabilizer leg  30 , in conjunction with the leg&#39;s fixed linkage  35 , to react to either extend to the ground or retract toward a closed position. The differential assembly  11  will allow the ground to stop the advancement of the stabilizer leg  30  by stopping the rotation of the drive screw  20 ,  21 . When the drive screw of one stabilizer leg stops, the differential assembly redirects the motor torque to the other stabilizer leg. The motor  12  may be operated remotely by electrical switches or other electrical controls. 
     It is understood that the above-described embodiment is merely illustrative of the application. Other embodiments may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.