Abstract:
Methods and systems for a multi-capacity vehicle lift system are provided. The system includes a lift assembly having a plurality of lift capacities and a load platform coupled to the lift assembly. The load platform includes a plurality of lift starting positions, each of the plurality of lift starting positions corresponding to a respective one of the plurality of lift capacities.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of the filing date of U.S. Provisional Application No. 60/974,964 filed on Sep. 25, 2007, entitled “Methods and Systems for Multi-capacity Vehicle Lift System,” which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     This invention relates generally to lift systems, and more particularly to methods and systems for vehicle lift systems having two or more lifting capacities. 
     At least some known above grade vehicle lift systems, especially those designed for lifting vehicles to a maintenance height, include a pair of runway tracks for positioning the vehicle, a base member for supporting the vehicle and vehicle lift system, and an expandable linkage system usually powered by a hydraulic cylinder or lead screw driving member to provide a lifting force. A ramp leading to each of the runway tracks permits a vehicle to be driven onto the vehicle lift system prior to being lifted. A height of the vehicle lift system and the vehicle ground clearance generally determines the configuration of the ramp. In general it is desirable to have the lowered height of the vehicle lift system be as low as possible. A low lowered height permits vehicles with a lower ground clearance to be driven onto the vehicle lift system without having to use long approach ramps. A higher height vehicle lift system or a vehicle with a low ground clearance requires a longer less sloped ramp. A vehicle lift system configured to a relatively low height may be limited in lifting capacity, however due to the size limitations and orientation imposed on the actuating mechanism by the low height. 
     If a greater lifting capacity is needed, the lowered height of the vehicle lift system typically becomes greater. This increased height requires longer approach ramps. However, the dimensions of a garage or shop may preclude a long ramp approach to the vehicle lift system. Therefore, space limitations may effectively place a limitation on the practical height of the vehicle lift system in the fully lowered position. 
     Generally, the actuating mechanism and the expandable linkage system are located within the space defined by the runway and the base. Positioning the actuating mechanism and the expandable linkage system outside of this space tends to inhibit access of the technician to the area under the vehicle to be worked on. 
     A vehicle lift system having an actuating mechanism that is sized and positioned to accommodate such limitations may be of sufficient capacity to be able to lift relatively smaller vehicles, however, to increase the vehicle lift system efficiency, larger vehicles should be accommodated as well. 
     It is desired to have a vehicle lifting system that has both a low lowered height as well as a high lifting capacity. 
     SUMMARY 
     In one embodiment, a multi-capacity vehicle lift system includes a lift assembly having a plurality of lift capacities and a load platform coupled to the lift assembly. The load platform includes a plurality of lift starting positions, each of the plurality of lift starting positions corresponding to a respective one of the plurality of lift capacities. 
     In another embodiment, a method of increasing the lift capacity of a lift device is provided. The lift device includes an expandable linkage coupled to a load platform, the expandable linkage includes an actuator coupled to the expandable linkage and provides a force to the expandable linkage. The method includes selecting a first starting position from a plurality of available starting positions for the actuator wherein each of the available starting positions corresponds to one of a plurality of lifting capacities and positioning the actuator in the selected first starting position wherein the expandable linkage is in a first collapsed position. 
     In yet another embodiment, a lifting device for a vehicle includes a first and second scissor units, each of which includes a base member and a load platform and for each scissor unit, a respective driving member assembly pivotally attached to a lever of the respective scissor unit, the driving member configured to be translated between a first starting position and a second starting position while the scissor units are in an initial collapsed position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side schematic view of an exemplary lift system in accordance with an embodiment of the present invention; 
         FIG. 2  is a side schematic view of the actuator assembly shown in  FIG. 1  in a first starting position; 
         FIG. 3  is a side schematic view of the actuator assembly shown in  FIGS. 1 and 2  in a second starting position; 
         FIG. 4  is a side schematic view of an actuator assembly in accordance with an embodiment of the present invention in a first starting position; 
         FIG. 5  is a side elevation view of a multi-capacity lift system actuating assembly in accordance with another embodiment of the present invention; and 
         FIGS. 6A and 6B  are side elevation views of a multi-capacity lift system actuating assembly in accordance with another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description illustrates the disclosure by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the disclosure, describes several embodiments, adaptations, variations, alternatives, and uses of the disclosure, including what is presently believed to be the best mode of carrying out the disclosure. The disclosure is described as applied to a preferred embodiment, namely, systems and methods for increasing the lift capacity of a lifting device. However, it is contemplated that this disclosure has general application to vehicle lift systems, jacks, positioners, and other machines that provide an application of force in vertical, horizontal, and a combination of orientations in industrial, commercial, and residential applications. 
       FIG. 1  is a side schematic view of an exemplary lift system  100  in accordance with an embodiment of the present invention. In the exemplary embodiment, lift system  100  includes a base  102  and a load platform  104  configured to move away from base  102  in a first direction  106 . Lift system  100  includes an expandable actuator linkage  108  mechanically coupled between load platform  104  and base  102  to facilitate load platform  104  moving away from base  102 . Lift system  100  also includes an actuator assembly  110  configured to provide a motive to expand actuator linkage  108 . Actuator assembly  110  includes a cam  112  including a positioning lobe  114 , a positioned lobe  116 , and a pivot point  118  that is offset from lobes  114  and  116 . Cam  112  is coupled to actuator linkage  108  at pivot point  118 . 
     Actuator assembly  110  also includes a driving member  120 , for example, but not limited to a piston and cylinder assembly or a lead screw assembly. Driving member  120  includes a first end  122  rotatably coupled to base  102  or actuator linkage  108 . Driving member  120  further includes a second end  124  rotatably coupled to positioned lobe  116 . Actuator assembly  110  also includes a positioning member  126  that includes a first end  128  coupled to actuator linkage  108  and a second end  130  rotatably coupled to positioning lobe  114 . 
     In the exemplary embodiment, expandable actuator linkage  108  comprises a pair of scissor linkages  132  and  134  (only pair  132  is shown in  FIG. 1 ) connected at a median pivot point  136 . Each of scissor linkages  132  and  134  includes a first linkage  137  pivotally and slidably connected at a lower end  138  to base  102 , and fixedly and pivotally connected at an upper end  140  to load platform  104 . A second linkage  142  is pivotally and slidably connected at an upper end  144  to load platform  104  and fixedly and pivotally connected at a lower end  146  to base  102 . Linkage  132  is connected to linkage  142  by median pivot point  136 . 
       FIG. 2  is a side schematic view of actuator assembly  110  (shown in  FIG. 1 ) in a first starting position. As used herein the first starting position includes positioning member  126  substantially fully retracted, cam  112  rotated fully counterclockwise (as viewed in  FIGS. 1 and 2 ), and driving member  120  located on a single side of load platform  104 . In the exemplary embodiment, cam  112  is substantially triangular in cross section. Cam  112  includes a positioning lobe  114 , a positioned lobe  116 , and a pivot point  118  that is offset from lobes  114  and  116  a distance  202 . Expandable actuator linkage  108  includes a first elongate aperture  204  configured to receive a first pin  206  coupled to pivot point  118  and a second elongate aperture  208  configured to receive a second pin  210  coupled to positioning lobe  114 . Positioning member  126  is coupled to positioning lobe  114  using second pin  210 . First elongate aperture  204  includes a longitudinal centerline  211  and second elongate aperture  208  includes a longitudinal centerline  213 . Longitudinal centerline  211  is aligned obliquely with respect to centerline  213 . 
     In the first starting position, positioning member  126  is substantially fully retracted such that pin  210  is positioned towards the right side of second elongate aperture  208 , cam  112  is rotated fully counterclockwise as viewed in  FIGS. 1 and 2  such that pin  206  is positioned towards the bottom right side of first elongate aperture  204 , and a longitudinal axis  212  of driving member  120  and base  102  form a first angle  214  with respect to each other. Also, in the first starting position, driving member  120  is located on a single side of load platform  104 , namely the underside. Because angle  214  is relatively shallow, only a small portion of the driving force generated by driving member  120  is useful in expanding actuator linkage  108  such that load platform  104  moves in direction  106  away from base  102 . 
       FIG. 3  is a side schematic view of actuator assembly  110  (shown in  FIGS. 1 and 2 ) in a second starting position. As used herein, the second starting position includes positioning member  126  substantially fully extended, cam  112  rotated fully clockwise (as viewed in  FIGS. 1 and 2 ), and driving member  120  extended at least partially through load platform  104 . In such a position, angle  214  introduces a relatively larger force component in direction  106  such that with the same driving member  120  system  100  delivers a greater force in direction  106  which translates into a capacity to raise a heavier load than when actuator assembly  110  is in the first starting position. 
     In operation, positioning member  126  is extended such that pin  210  and positioning lobe  114  are moved along second elongate aperture  208 . Pin  206  is driven along first elongate aperture  204 , which because centerline  211  is oriented obliquely with respect to centerline  213 , positioned lobe  116  is rotated clockwise and away from base  102 . Such rotation causes driving member  120  to rotate counterclockwise increasing angle  214  with respect to base  102 . The rotation of cam  112  also extends a portion of driving member  120  and cam  112  through load platform  104  such that during extension of driving member  120 , the portion of driving member  120  and cam  112  extend above load platform  104 . 
     The multi-capacity capability of the lift system described in accordance with embodiments of the present invention permit a single lift system to adjust to the lift needs of a user while maintaining a low profile and eliminating a need to cut a pit into a concrete floor. An increased lift capability provides a user an ability to lift vehicles with a low ground clearance, and typically lower weight in a first configuration and to lift medium duty trucks and heavier commercial-style vehicles that typically have a higher ground clearance in the second configuration. In use, extending a portion of driving member  120  and cam  112  through load platform  104  does not interfere with the vehicle to be lifted because actuator assembly  110  is maintained in the first position until the vehicle is driven onto load platform  104 . Actuator assembly  110  is then reposition to the second position wherein a portion of driving member  120  and cam  112  extend through load platform  104 . However, because of the ground clearance of most heavier vehicles, the portion of driving member  120  and cam  112  extending through load platform  104  will not reach the undercarriage or chassis of the vehicle. In an instance of lifting a smaller vehicle, there is no need to extend the portion of driving member  120  and cam  112  through load platform  104  because system  100  has sufficient capacity in the first position to lift the relatively smaller vehicle. 
       FIG. 4  is a side schematic view of an actuator assembly  402  in accordance with an embodiment of the present invention in a first starting position. As used herein, the first starting position includes a positioning member  404  substantially fully retracted, a cam  406  rotated fully counterclockwise (as viewed in  FIG. 4 ), and a driving member  408  located above a base  409 , such as a floor of a repair shop. In the exemplary embodiment, cam  406  is substantially triangular in cross section. In an alternative embodiment, cam  406  is a straight linkage. Cam  406  includes a positioning lobe  412 , a positioned lobe  414 , and a pivot point  416  that is offset from lobes  412  and  414  a distance  418 . An expandable actuator linkage  420  includes a first elongate aperture  422  configured to receive a first pin  424  coupled to pivot point  416  and a second elongate aperture  426  configured to receive a second pin  428  coupled to positioning lobe  412 . Positioning member  404  is coupled to positioning lobe  412  using second pin  428 . First elongate aperture  422  includes a longitudinal centerline  430  and second elongate aperture  426  includes a longitudinal centerline  432 . In the exemplary embodiment, longitudinal centerline  430  is aligned obliquely with respect to centerline  432 . 
     In the first starting position, positioning member  404  is substantially fully retracted such that pin  428  is positioned towards the left side of second elongate aperture  426 , cam  406  is rotated fully counterclockwise as viewed in  FIG. 4  such that pin  424  is positioned towards the lower right side of first elongate aperture  422 , and a longitudinal axis  434  of driving member  408  and load platform  410  form a first angle  436  with respect to each other. Also, in the first starting position, driving member  408  is located on a single side of base  409 , namely the upper side. Because angle  436  is relatively shallow, only a small portion of the driving force generated by driving member  408  is useful in expanding actuator linkage  420  such that a first end  438  of driving member  408  moves in a direction  440  away from load platform  410 . 
     A second starting position includes positioning member  404  substantially fully extended, cam  406  rotated substantially fully clockwise, and driving member  408  extended at least partially downwardly through or past base  409  below floor level. In such a position, angle  436  introduces a relatively larger force component in direction  440  such that with the same driving member  408 , system  100  delivers a greater force in direction  440  which translates into a capacity to raise a heavier load than when actuator assembly  402  is in the first starting position. 
     In operation, positioning member  404  is extended such that pin  428  and positioning lobe  412  are moved along second elongate aperture  426 . Pin  424  is driven along first elongate aperture  422 , which because centerline  422  is oriented obliquely with respect to centerline  432 , positioned lobe  116  is rotated clockwise and away from load platform  410 . Such rotation causes driving member  408  to rotate counterclockwise increasing angle  436  with respect to load platform  410 . The rotation of cam  406  also extends a portion of driving member  408  and cam  406  through or past base  409  such that during extension of driving member  408 , the portion of driving member  408  and cam  406  extend below base  409 . 
       FIG. 5  is a side elevation view of a multi-capacity lift system actuating assembly  500  in accordance with another embodiment of the present invention. Actuating assembly  500  includes a driving member  502  having a longitudinal axis  504  coupled between an anchor  506  and a positioning linkage  508 , which is further coupled to an expandable linkage assembly  510 . A first travel stop  512  maintains driving member  502  in a first starting position  514 . A second travel stop  516  maintains driving member  502  in a second starting position  518  (shown in dotted outline in  FIG. 5 ). In first starting position  514 , a distal end  520  of driving member  502  remains on a single side of a load platform  522 . 
     During operation, a low or high capacity lift is selected by a user. Alternatively, the lift capacity is automatically selected based on a sensed parameter of a load (not shown) on load platform  522 , for example, but not limited to a weight of the load, a total height of the load, a gap distance between load platform  522  and an underside of the load, and a length or wheelbase of the load. If the lower lift capacity is selected, first travel stop  512  is in a position to prevent rotation of positioning linkage  508 . Driving member  502  extending bears against first travel stop  512  and a first driving force is transmitted though positioning linkage  508  to expandable linkage assembly  510  to expand linkage assembly  510 , which in turn moves load platform  522  in a direction  524  at a first lift capacity. Alternatively, if the higher lift capacity is selected, first travel stop  512  is in a position to permit rotation of positioning linkage  508  until it engages second travel stop  516 . Driving member  502  extending rotates positioning linkage  508  from first starting position  514  to second starting position  518 . The rotation of positioning linkage  508  permits driving member  502  to rotate to second starting position  518 , where a portion of driving member  502  extends above load platform  522 . In an alternative embodiment, none of driving member  502  extends above load platform  522 . In the exemplary embodiment, one or more movable plates  526  extend above load platform  522  to cover an aperture through which driving member  502  extends. In an alternative embodiment, driving member  502  extends past load platform  522  without passing through load platform  522  such that plates  526  are not necessary and are not used. After a predetermined amount of extension of driving member  502 , positioning linkage  508  bears against second travel stop  516  and a second driving force is transmitted though positioning linkage  508  to expandable linkage assembly  510  to expand linkage assembly  510 , which in turn moves load platform  522  in a direction  524  at a second lift capacity. Because of the change in geometry of expandable linkage assembly  510  and actuator assembly  500 , second lift capacity is greater than first lift capacity permitting heavier loads, such as trucks to be lifted using a lift system having the same starting height as when the first capacity lift is selected. Because heavier loads are generally associated with a larger ground clearance, driving member  502  extending above load platform during a lift will not engage the underside of the truck. 
       FIGS. 6A and 6B  are side elevation views of a multi-capacity lift system actuating assembly  600  in accordance with another embodiment of the present invention. Actuating assembly  600  includes a driving member  602  having a longitudinal axis  604  coupled between an anchor  606  and a positioning linkage  608 , which is further coupled to an expandable linkage assembly  610 . A travel stop  612  in a first position  616  maintains positioning linkage  608  in a locking position that prevents positioning linkage from rotating in a clockwise direction  618  about pin  620 . 
     During operation in first position  614 , driving member  602  is extended such that a distal end  622  bears against positioning linkage  608  transferring the force generated by the extending driving member  602  to expandable linkage assembly  610 . The force imparted to expandable linkage assembly tends to expand the linkage assembly  610  in a direction  624  at a first relatively low lifting capacity. The lifting capacity is related to an angle  626  between driving member  602  and direction  624 . In first starting position  614  a relatively smaller portion of the force generated by driving member  602  is applied in direction  624 . 
     Travel stop  612  is movable to a second position such that it does not prevent rotation of positioning linkage  608  to a second position shown in  FIG. 6B . As driving member  602  extends, positioning linkage  608  rotates in direction  618  to a fully rotated position. In alternative embodiments, intermediate stops may be used to provided additional stop locations. With positioning linkage  608  in the fully rotated position, further extension of driving member  602  begins applying a force to distal end  622 , which bears against positioning linkage  608  transferring the force generated by the extending driving member  602  to expandable linkage assembly  610 . The force imparted to expandable linkage assembly tends to expand the linkage assembly  610  in a direction  624  at a second relatively high lifting capacity. The lifting capacity is related to an angle  628  between driving member  602  and direction  624 . In second starting position  630 , a relatively larger portion of the force generated by driving member  602  is applied in direction  624 . In the exemplary embodiment, in second starting position  630 , a portion of driving member extends past or through load platform  632  to permit a high lift capacity while maintaining a relatively low starting height for load platform  632  during load lifting. 
     The above-described methods and systems of lifting a load are cost-effective and highly reliable. The methods and systems facilitate operating a lift system capable of accommodating the dimensions of smaller vehicles having a lighter weight while being capable of lifting relatively larger and heavier loads where physical dimensions are less of a concern in a cost-effective and reliable manner. 
     While embodiments of the disclosure have been described in terms of various specific embodiments, those skilled in the art will recognize that the embodiments of the disclosure can be practiced with modification within the spirit and scope of the claims.