Abstract:
A modular inground lift is supported by the lift bay floor. The lift includes self contained modules which have their own power units. A telescoping cylinder and locking leg allow the depth of the lift to be shallower than before. The use of VFD to control the motors allows monitoring of the loads, both during raising and lowering. The modular lift includes integral rebar to provide the structural connection with the lift bay floor.

Description:
BACKGROUND OF THE INVENTION  
       [0001]    This application claims priority from U.S. Provisional Patent Application Serial No. 60/412,483, filed Sep. 20, 2002, which is incorporated herein by reference. This application hereby incorporates by reference U.S. patent application Ser. No. 09/884,673, filed Jun. 19, 2001, titled Removable Cylinder Arrangement For Lift, U.S. patent application Ser. No. 10/055,800, filed Oct. 26, 2001, titled Electronically Controlled Vehicle Lift And Vehicle Service System, U.S. patent application Ser. No. 10/056,985, filed Jan. 25, 2002, titled System for Detecting Liquid In An Inground Lift, and U.S. patent application Ser. No. 10/123,083, filed Apr. 12, 2002, titled Method And Apparatus For Synchronizing A Vehicle Lift, all of which are commonly owned herewith. 
     
    
     
         [0002]    Heavy duty inground lifts are well known in the art. Such lifts typically have at least a pair of spaced apart cylinder located at least partially within a below ground pit. It is also know to have more than two spaced apart jacks in a single bay.  
           [0003]    Depending on the needs, typically one of these jacks is fixed in place and the others are moveable longitudinally, within an elongated pit. The moveable jack is typically carried by a trolley which is supported by spaced apart tracks located slightly below the level of the floor or other surface surrounding the lift. It is known for the lift housing to be made from concrete walls and floor poured in place in a trench, or to be a self contained containment housing which in disposed in a trench. In either case, the tracks are disposed atop the walls in a manner that the force from the load on the jack is transmitted to the housing walls, and through the housing walls to the housing floor, which in turn is supported by the soil and gravel located in the pit. In this configuration, it is the bottom of the pit that provides the support for the jacks to carry the vehicle.  
           [0004]    Single stage cylinders require the lift pit to be dug over ten feet deep. The construction of a concrete pit can take about three months due to the cure time of the concrete and the sequential timing of pouring the pit floor, pit walls and the floor. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0005]    The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings:  
         [0006]    [0006]FIG. 1 is a perspective, partially cut-away view of a heavy duty inground lift according to teachings of the present invention.  
         [0007]    [0007]FIG. 2 is a perspective, exterior view of the inground lift of FIG. 1.  
         [0008]    [0008]FIGS. 3 and 4 illustrate typical equipment foundation requirements.  
         [0009]    [0009]FIG. 5 includes a top, side, and end view of the housing, and an enlarged fragmentary view of overlapping sections of the housing of the inground lift of FIG. 1.  
         [0010]    [0010]FIG. 6 is a cross-sectional view through the housing of the inground lift of FIG. 1, showing the carriage supported by the side tracks.  
         [0011]    [0011]FIG. 7 is a cross-sectional view through a telescoping cylinder of the inground lift of FIG. 1.  
         [0012]    [0012]FIG. 8 is a diagrammatic illustration of a hydraulic circuit of the inground lift of FIG. 1.  
         [0013]    [0013]FIG. 9 is a perspective view of the telescoping locking leg of the inground lift of FIG. 1.  
         [0014]    [0014]FIG. 10 is a perspective view of the telescoping locking leg of FIG. 9.  
         [0015]    [0015]FIG. 11 is an enlarged, fragmentary view of the upper locking mechanism illustrated at detail A of FIG. 10.  
         [0016]    [0016]FIG. 12 is a top view of the upper locking mechanism of FIGS. 10 and 11.  
         [0017]    [0017]FIG. 13 is a fragmentary cross-sectional view of the telescoping locking legs taken along line B-B of FIG. 12.  
         [0018]    [0018]FIG. 14 is a perspective view of the control panel of the of the inground lift of FIG. 1.  
         [0019]    [0019]FIG. 15 is a perspective view of an alternate control panel of the inground lift of FIG. 1.  
         [0020]    [0020]FIG. 16 illustrates rate of adjustment versus the angle of the joystick.  
         [0021]    Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    Referring now to the drawings in detail, wherein like numerals indicate the same elements throughout the views, FIG. 1 is a is a perspective, partially cut-away view of a heavy duty inground lift  2  including two modules  4  and  6 , each having its own respective power unit (seen only in module  4  as power unit  8 ). The depicted embodiment has a capacity of 30,000 lbs. Lift  2  includes control panel  10 , located in any desired location.  
         [0023]    Modules  4  and  6  includes respective telescoping jacks  12  and  14 , the construction and operation of which is substantially the same, although jack  12  is moveable longitudinally within housing  16  while jack  14  is fixed within housing  18 . The mechanism of jack  12  that allows longitudinal movement is well known in the art. Jack  12  is carried by carriage or trolley  20 , as seen also in FIG. 6, and includes wheels  22  supported by spaced apart tracks  24  and  26 . Tracks  24  and  26  are each an inwardly opening channel having a generally “C” shaped cross section, in which the wheels  22  are located. The lower, horizontal legs of tracks  24  and  26  surmount a member having a 90° cross section, with one leg  28  underlying the track and a longer, downwardly depending leg  30  oriented generally vertically. Leg  30  is secured to sidewalls  16   a  of housing  16 .  
         [0024]    Carriage  20  is moved by chains  32  which are ultimately driven by driven by the hydraulic motor and gear reducer assembly  34  located as appropriate, in the depicted embodiment at one end of housing  16 . Moving shingles  36  travel with carriage  20 , covering the top of housing  16  regardless of the location of jack  12 . The horizontal position of jack  12  is monitored by any appropriate device, such as string potentiometer, diagrammatically illustrated as  38 , secured at one end to a fixed location.  
         [0025]    In the present invention, all the support for the load carried by jacks  12  and  14  is provided the lift bay floor  40 , rather than the sidewalls  16   a  and the bottom of the trench. The present invention includes structure which interact in conjunction with the lift bay floor  40  to transfer substantially all of the load to the lift bay floor  40 . In the depicted embodiment, floor  40  is constructed to have the necessary structural capacity with the necessary underlying supporting layer providing the foundational support.  
         [0026]    Since sidewalls  16   a  (including the endwalls) do not carry the load from jack  12 , they are not vertically load bearing. The sidewalls  16   a  are thus constructed to resist external side and bottom loads to maintain the integrity of the cavity, and to contain fluids as well as to keep groundwater out. A liquid detecting system, as disclosed in U.S. patent application Ser. No. 10/056,985 for System for Detecting Liquid In An Inground Lift may be utilized.  
         [0027]    As can be seen in FIGS.  1 - 6 , sidewalls  16   a  have been strengthened, in the depicted embodiment by the inclusion of a plurality of spaced ribs  42  extending vertically from proximal the bottom  16   b  to proximal the upper edges of sidewalls  16   a . Although the present invention contemplates any side wall configuration adequate to resist the side and bottom loading, the depicted embodiment includes ribs  42  having a tapered section  42   a  at their respective upper ends, blending back into the generally planar upper edges of sidewalls  16   a . In the depicted embodiment, a slit  42   b  is formed in section  42   a  to accommodate material movement resulting from the forming process. The number, spacing and location of ribs may vary as appropriate.  
         [0028]    As seen in FIG. 5, in the depicted embodiment: housing  16  also includes an internal frame  16   c  which provides support to sidewalls  16   a . Frame  16   c  may be located in any desired location to provide such support, including for example, proximal the lower portion of sidewalls  16   a.    
         [0029]    Also seen in FIG. 5, in the depicted embodiment: housing  16  is made of sections which overlap vertically, such as shown at  44 , which are skip welded. The ends  16   d  are identical sections, including two 90° corners and “legs” of different length extending therefrom, with side sections welded to each leg. The overall length of housing  16  is selected as desired and the appropriate number of side panels assembled together with the ends  16   d.    
         [0030]    A coating is applied to the inside and outside of housings  16  and  18 , which comprises a thin (about ⅛ inch) high dielectric material. As will be readily appreciated, the coating resists corrosion of the steel housing  16 . The coating is also beneficial in allowing the use of skip welding, sealing the seams in between welds.  
         [0031]    Referring to FIGS.  2 - 4 , as mentioned above, lift  2  includes structure which interact in conjunction with the lift bay floor  40  to transfer substantially all of the load to the lift bay floor  40 . In the depicted embodiment, floor  40  is constructed to have the necessary structural capacity with the necessary underlying supporting layer providing the foundational support. In the depicted embodiment, housings  16  and  18  include members  46 , including reinforcing bars (also known as rebar), extending from the upper portion of the housings.  
         [0032]    The physical characteristics of such members, such as location, size, quantity and orientation, are determined so as to provide the necessary interaction between them and the surrounding lift bay floor  40  to provide the load transfer required. As seen in FIGS. 3 and 4, rebar is arranged in a pattern sufficient to provide the necessary structural strength and integrity for lift bay floor  40  to support lift  2  with jacks  12  and  14 . FIGS. 3 and 4 illustrate the typical equipment foundation requirements, including the placement of gravel and other typical material. Although rigid insulation is illustrated adjacent the housings  16  and  18 , such is not necessarily placed there. The thickness of the surrounding lift bay floor  40  slopes from its nominal thickness to an increased thickness proximal the housings  16  and  18 . Although FIG. 3 illustrates pea gravel disposed well beyond the sides of the housing  16 , extending beyond the top of the trench in which housing  16  is disposed, such is not necessarily placed there.  
         [0033]    With such construction, full support of lift  2  and jacks  12  and  14  is provided by the lift bay floor  40 . The modules, each being self contained, allows great flexibility in locating and installing the lift. Since the support is provided by the lift bay floor  40 , there is no need to pour a structural concrete floor in the pit bottom for lift support, wait several weeks for it to cure, pour pit walls, wait several weeks for curing, and then pour the lift bay floor also followed several weeks for curing. The present invention allows the inground lift to be installed with a single pour, significantly reducing the installation time. It also makes retrofitting old lifts much easier.  
         [0034]    Returning to FIG. 1, modules  4  and  6  each include a respective power unit, only seen as  8  in FIG. 1 for module  4 . In the depicted embodiment, power unit  8  is fixedly mounted, and does not move with jack  12 . Power unit  8  includes a motor and hydraulic pump which supplies hydraulic fluid to and from telescoping cylinder  48 . Jack  12  includes telescoping locking leg  50 , which is connected at the top to saddle  52  which is carried by cylinder  48 . Locking leg  50  is designed to hold saddle  52  (and any vehicle thereon) in place in the event of loss of pressure within cylinder  48 . Jack  14  has the same cylinder and locking leg construction.  
         [0035]    Referring to FIG. 7, cylinder  48  includes three concentric sections  48   a ,  48   b  and  48   c . Section  48   a  includes a flange  48   a ′ which is carried by carriage  20 . Upon the application of pressurized hydraulic fluid to the internal cavity  54  of cylinder  48 , sections  48   b  and  48   c  extend in synchronized motion from section  48   a . Synchronized relative movement of ail sections of cylinder  48  avoids the bump that typically occurs at the transition between sections when a multiple section cylinder extends one section at a time, and avoids the control difficulties associated therewith, such as stage capacity issues, speed changes, abrupt stops.  
         [0036]    The fluid pressurizes cavities  54 ,  54   a  and  54   b , which are in communication with each other. Synchronous motion results from fluid located in cavity  48   d  being forced into internal cavity  56 , which is not in fluid communication with cavities  54 ,  54   a  and  54   b , through passageways  56   a . This fluid forces section  48   c  to extend the same amount in order to maintain internal cavity  56  at a constant volume. Since the annular area of cavity  48   d  is equal to the annular area of the difference between the inner diameter of section  48   b  and the inner diameter of section  48   c , the linear displacement of sections  48   b  and  48   c  are equal. Spring loaded valve  58  includes stem  58   a  which contacts wall  60  when the sections  48   a ,  48   b  and  48   c  are collapsed within each other, thereby equalizing the pressure between cavities  54 ,  54   a  and  54   b , and cavity  56 .  
         [0037]    [0037]FIG. 8 diagrammatically illustrates a hydraulic circuit, generally indicated at  62 , of the inground lift  2  of this depicted embodiment. shown in FIG. 1. Motor  64  drives hydraulic pump  66 . Pressure relief valve  68  prevents overpressure. When motor  64  is on, rotating to raise jack  12 , fluid flows past air pilot operated check valve  70 , in the position shown, past velocity fuse  72  (which prevents hydraulic pressure from flowing from cylinder  58  too fast in the event of a leak downstream of fuse  72 ) and into cavity  54  of cylinder  48 , thereby raising it. Each motor/pump is controlled by a respective variable frequency drive (VFD) motor controller to effect raising and lowering of each lift.  
         [0038]    Jack  12  is powered down. Valve  70  is moved to the down position, and motor  64  is energized to run pump  66  in the opposite direction, thereby pulling fluid from cylinder  54 . Valve  74  prevents pump  66  from removing the fluid too fast, preventing a vacuum.  
         [0039]    As shown in FIGS.  9 - 13 , each jack includes a respective telescoping locking leg  50 , which prevents unintended downward movement of the lift. The telescoping aspect of telescoping locking leg  50  allows an overall shorter length as with telescoping cylinder  48 , thereby reducing the depth of the trench that has to be dug for modules  4  and  6 .  
         [0040]    Telescoping locking leg  50  is carried by flange  82  extending from the outside of cylinder  48 , and includes upper leg  76  which is telescopingly disposed relative to and, in the depicted embodiment, within lower leg  78 . Lower locking mechanism  80  is carried by flange  82 , and guides lower leg  78  as it moves through the opening (not numbered) as lift  12  is raised and lowered. Lower locking mechanism  80  includes pivoting latch  84  which is normally biased into engagement with a series of vertically aligned windows and steps  86 , resembling a ladder, by spring  88 . Latch  84  is Engagement of latch  84  with any of the steps  86  prevents lift  12  from lowering beyond that step, thereby providing a positive mechanical lock, preventing downward movement of the lift. In order to lower the lift intentionally, latch  84  is held in its disengaged position by actuation of air cylinder  90 .  
         [0041]    Upper leg  76  includes a plurality of stop blocks  92  disposed as pairs on opposite sides of upper leg  76 . Lower edge  92   a  of each block  92  is generally flat and perpendicular to the vertical sides of upper leg  76 , while upper edge  92   b  of each block  92  is inclined. Upper end  94  of lower leg  78  includes a flange  96  which upper locking mechanism  98 . Upper locking mechanism  98  includes two spaced apart pivotably mounted latches  100  and  102  which are pivotably mounted to flange  96  by pivots  104 . Latches are biased toward each other by spring  106  into an engaged or locked position as best seen in FIG. 12. In the engaged position, the edges of latches  100  and  102  are parallel with the corresponding adjacent surface of upper leg  76 . As upper leg  76  is extended, upper edges  92   b  of each pair of blocks will force latches  100  and  102  outwardly as blocks  92  pass. Latches  100  and  102  will return to the engaged position once they reach the lower edges  92   a  of blocks  92 .  
         [0042]    As lift  12  is raised, upper leg  76  will be the first leg to move, traveling upwardly by virtue of being connected to saddle  52 . Stops  92  are spaced about 24 inches down from the top of upper leg  76  and the safety stops are not needed before upper leg  76  has extended that far. Once the extension of upper leg  76  has caused latches  100  and  102  to reach the last set of blocks  92 , with latches  100  and  102  in the engaged position, upper leg  76  will stop telescoping from lower leg  78  and lower leg  78  will begin extending from lower locking mechanism  80 . Upper leg  76  is interconnected to lower leg  78  by rod  108  which allows movement therebetween until upper leg  76  has extended the desired/designed amount. At that point, rod will pull lower leg  78  upward as saddle  52  pulls upper leg  76  upward with it.  
         [0043]    In order to lower the lift intentionally, latches  100  and  102  are held spaced apart, constrained from over travel by stops  110  and  112  by actuation of air cylinder  114 , which is pivotably connected to each latch  100  and  102 .  
         [0044]    When motor  64  is energized to raise jack  12 , the configuration of lower locking mechanism and upper locking mechanism permits the upward movement without applying any pressure, with latch  84  periodically engaging steps  86  and latches  100  and  102  engaging lower blocks  92 . When motor  64  is energized to lower jack  12 , air cylinders  90  and  114  are energized simultaneously and latches  84 ,  100  and  102  are held in disengaged positions allowing telescoping locking leg  50  to retract.  
         [0045]    The vertical positions of jacks  12  and  14  are respectively monitored by any appropriate devices, such as string potentiometers (not shown).  
         [0046]    Referring to FIG. 14, there is shown a perspective view of the control panel  10  of lift  2 . Control panel  10  includes display  116 , joy stick  118 , and key pad  120 . An alternate control panel is illustrated in FIG. 15.  
         [0047]    In the depicted embodiment, key pad  120  comprises four electric switches or keys generally corresponding to the keys disclosed in U.S. patent application Ser. No. 10/055,800 for Electronically Controlled Vehicle Lift And Vehicle Service System. In the embodiment depicted in this application, the controls disclosed in U.S. patent application Ser. No. 10/055,800 and U.S. patent application Ser. No. 10/123,083, are used herein, with the appropriate modification to accommodate the operation of the present lift. For example, since the present lift may include an odd number of lifts, synchronization may be done in many different ways, such as controlling two of the lifts relative to one.  
         [0048]    When the control of lift  2  is in the operation mode, rather than an information mode, the lift  2  may be placed in the positioning mode or the lifting mode. In the positioning mode, the joystick is used to place the adapters in contact with the axle or other part of the vehicle being lifted. This involves the horizontal positioning of any horizontally moveable lift, such as jack  12 , and the vertical positioning of each jack to the proper vehicle contacting height. After proper positioning, the control is switched to the lifting mode and the vehicle is lifted. In the positioning mode, the control allows selection between horizontal and vertical positioning for any jack which is horizontally moveable, and selection of vertical positioning for any fixed jack.  
         [0049]    In the depicted embodiment, positioning is controlled by the joystick in combination with the key pad for appropriate mode selections. In the two jack configuration depicted, there are three screens: one for vertical positioning of the front, fixed jack, one for vertical positioning of the rear jack, and one for horizontal positioning of the rear jack.  
         [0050]    In the depicted embodiment, to set the position for the rear jack, the control system is scrolled to the appropriate screen, and the joystick is used to make the adjustment. In the horizontal positioning mode, the VFD controls the horizontal positioning motor to move the jack  12  to the desired horizontal position. Using the position sensor, such as the output of the string potentiometer, the control can determine the horizontal position. The control may be programmed with specific horizontal locations for locating the jack, which can remember frequently used horizontal locations such as corresponding to wheelbase dimensions. This may be done, for example, by programming stop points at which the jack is stopped, and following release and reengagement of the deadman joystick, caused to move until the next programmed stop location is reached, going through this process until the desired programmed stop location is attained. With appropriate safety safeguards, the control could drive the lift to a preprogrammed horizontal position rather than stopping at each point. In one embodiment, all programmed stop locations are set to the maximum position, rendering them ineffective.  
         [0051]    Since the control is done through the respective VFD for each module, the current to the motor may be controlled precisely. The control can monitor the current draw and stop the movement in the event that too much current is drawn, such as in an over torque situation if the lift encounters an obstruction or if the lift reaches either end of its horizontal travel and is physically unable to move further. If an over current condition is encountered, the lift control shuts down operation and goes into a troubleshooting mode using screen displays to guide the operator to resolution of the problem.  
         [0052]    Once the jack  12  is in the proper horizontal position, the vertical position of jack  12  is adjusted. The control is toggled to the appropriate mode, and the joystick is used to raise the saddle. The same VFD drives the vertical movement motor and the control torque limits the motor by limiting current to prevent any lifting of the vehicle with just the one lift. This allows the operator to bring the adapters into the proper contact with the axle.  
         [0053]    The other jacks are then adjusted to the appropriate position. In the depicted embodiment, the control is switched to position front jack  14  vertically to bring the adapters into the proper contact with the axle. The torque is limited by limiting the current to prevent any lifting of the vehicle.  
         [0054]    Once the jacks are in proper position, the control is switched to the lifting mode. Since for most vehicles, the axles are not in the same plane, the control establishes an offset for maintaining a level datum referenced to the vehicle, using the position information indicated by each jack&#39;s vertical position sensor, in the depicted embodiment a string potentiometer. It is noted that any suitable position sensor or control algorithm to determine position may be used.  
         [0055]    In the lifting mode, each jack may be controlled individually, such as when there is a need to raise one axle relative to the other. The default lifting mode, though, is the raising of all jacks synchronously. In the default “all” mode, the joystick is moved to raise or lower all lifts together. Preprogrammed heights may be provided. In the lift mode, the VFD is not current limited. Although not as accurate as current limited control, each power unit has its own hydraulic relief valve.  
         [0056]    The rate of adjustment made by the joystick varies with the angle of the joystick, as seen in FIG. 16. The rate of adjustment is programmable as desired.  
         [0057]    To lower the lifts, the respective VFDs of each module drives the motors in reverse. In one embodiment, each motor is driven to matching speeds. Other control algorithms may be used. For example, the approximate load could be determined by the current and speed. Different down gains could be used in the control algorithm.  
         [0058]    In summary, numerous benefits have been described which result from employing the concepts of the invention. The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described in order to best illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.