Abstract:
A quick-rise hydraulic lifting mechanism includes a lift arm, the lift arm being pivotable about an axis; a hydraulic actuator operably connected to the lift arm, the hydraulic actuator having an oil vacuum relief; and a mechanical actuator operably attached to the lift arm, the mechanical actuator comprising: a ratchet mechanism; and, an articulated linkage connecting the ratchet mechanism to the lift arm, wherein the articulated linkage comprises a pull bar, a push bar, and a pivotable link interconnecting the pull bar and the push bar, the pull bar being operably connected to the ratchet mechanism, the push bar being operably connected to the lift arm.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to hydraulic lifting jacks. More specifically, the present invention relates to a hydraulic jack with a mechanical linkage that raises the jack quickly when the jack is under no load or light load.  
       BACKGROUND OF THE INVENTION  
       [0002]     Conventional portable lifting jacks typically comprise a wheeled frame, a lifting arm retractably received in the frame, a hydraulic pump for driving the lifting arm, and a handle connected to the hydraulic pump. A hydraulic cylinder is disposed at a front side of the hydraulic pump. A hydraulic shaft is extendable from and retractable in the hydraulic cylinder. A rear end of the hydraulic shaft is movably fitted in the hydraulic cylinder. A front end of the hydraulic cylinder is connected with the lifting arm via a link arm.  
         [0003]     The hydraulic pump generally comprises a multipurpose block having at least one oil chamber and a plurality of oil chambers defined therein, a releasing device disposed in a release bore defined in a rear side of the multipurpose block, a piston cylinder disposed in a piston bore defined in the rear side of the multipurpose block, and a hydraulic cylinder securely connected with the multipurpose block at a threaded hole defined in a front side of the multipurpose block. When a user swings the handle manually, the lifting arm is driven by the hydraulic pump to move pivotally between a horizontal direction and an inclined direction. One prior art portable lifting jack is disclosed in U.S. Pat. No. 4,018,421.  
         [0004]     One problem with the prior art lifting jacks is that, although the jack provides great mechanical advantage in lifting heavy loads, the lifting arm is actuated via the hydraulic cylinder, even when the jack is not loaded. Because of the high mechanical advantage, the lifting arm raises slowly even under no-load lifts.  
         [0005]     There is a need for a portable lifting jack that provides a high mechanical advantage in lifting heavy loads yet can be raised quickly when not loaded. Accordingly, the present invention is hereby presented.  
       SUMMARY OF THE INVENTION  
       [0006]     One advantage of the present invention is achieved by providing a hydraulic lifting jack comprising a mechanical linkage that can be utilized when raising the jack under little or no load.  
         [0007]     Another advantage of the present invention is achieved by providing a hydraulic lifting jack comprising a conventional hydraulic cylinder that is utilized in raising the lifting arm when the jack is under a heavy load.  
         [0008]     Yet another advantage of the present invention is realized by providing a hydraulic lifting jack that has a vacuum relief port operably connecting the oil reservoir to the high pressure side of the hydraulic cylinder. The vacuum relief port allows oil from the oil reservoir to enter the space behind the hydraulic cylinder when the lifting arm/hydraulic cylinder is raised under no load.  
         [0009]     These and other advantages are realized by providing a quick rise hydraulic jack comprising: a lift arm, a hydraulic actuator, and a mechanical actuator, the hydraulic actuator comprising: a hydraulic cylinder having an extendible piston rod; an oil reservoir; a drive pump operably connected to the hydraulic cylinder, the drive pump comprising a drive cylinder and a drive piston; a suction-discharge valve operably connecting the oil reservoir, the drive pump, and the hydraulic cylinder during hydraulic-actuated lifting; a drive pump over-pressure relief valve operably connecting the drive pump and the oil reservoir; and, an oil vacuum relief valve operably connecting the oil reservoir and the hydraulic cylinder, the oil vacuum relief valve allowing oil to flow from the oil reservoir into the hydraulic cylinder during mechanically-actuated lifting; the lift arm being operably connected to the piston rod by a pin, the lift arm being pivotable about an axis; and the mechanical actuator comprising: a ratchet mechanism and an articulated linkage connecting the ratchet mechanism to the lift arm, wherein, the articulated linkage is connected to the lift arm by the same pin that connects the piston rod to the lift arm. 
     
    
     SUMMARY OF THE DRAWINGS  
       [0010]      FIG. 1  is a perspective view of a no-load quick rise hydraulic lifting mechanism, in accordance with a preferred embodiment of the present invention.  
         [0011]      FIG. 2  is a second perspective view of the lifting mechanism of  FIG. 1 , shown with internal components in dotted lines.  
         [0012]      FIG. 3  is a top plan view of the lifting mechanism of  FIG. 1 .  
         [0013]      FIG. 4  is a bottom view of the lifting mechanism of  FIG. 1 .  
         [0014]      FIG. 5  is a longitudinal cross-sectional view of the lifting mechanism of  FIG. 1 .  
         [0015]      FIG. 6  is a top plan view of a hydraulic actuator.  
         [0016]      FIG. 7  is a cross-sectional view through the longitudinal center line  7 - 7  of  FIG. 6 .  
         [0017]      FIG. 8  is a sectional view through line  8 - 8  of  FIG. 6 .  
         [0018]      FIG. 9  is a cross-sectional view through line  9 - 9  of  FIG. 6 .  
         [0019]      FIG. 10  is a side view of the lifting mechanism of  FIG. 1 , shown with portions of the side frame members removed.  
         [0020]      FIG. 11  is a side schematic view of a mechanical actuator portion of the lifting mechanism. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     The  FIGS. 1-5  illustrate a preferred embodiment of a quick rise hydraulic lifting mechanism or jack  10 . The jack  10  comprises a frame  12  formed of a plurality of frame members. The frame  12  is attached to a plurality of wheels  14 , such that the jack can be wheeled into a desired location. A handle  16  is connected to the rear end of the jack  10 . Operation of the handle  16  raises lift arm  18 , located near the front of the jack  10 .  
         [0022]     The jack  10  comprises dual mechanisms for raising the lift arm  18 , a hydraulic actuator  20 , and a mechanical actuator  80 . The hydraulic actuator  20  provides greater mechanical advantage in raising the lift arm  18  than the mechanical actuator  80 . However, the mechanical actuator  80  raises the lift arm  18  faster than the hydraulic actuator  20 . As such, the mechanical actuator  80  is preferably utilized to raise the lift arm  18  when the lift arm  18  is under no load or a light load, and the hydraulic actuator  20  is utilized to raise the lift arm under a heavier load.  
         [0023]     Although any type of hydraulic actuator  20  is contemplated for use in the present invention, a preferred embodiment of a hydraulic actuator  20  is described hereinafter. As best illustrated in  FIGS. 6-9 , the hydraulic actuator  20  comprises a hydraulic cylinder  22  and a hydraulic piston  24 . The hydraulic piston is connected to piston rod  26 , which extends forwardly from the hydraulic cylinder  22 . The forward end of the piston rod  26  is connected to the lift arm  18  via connector pin  29 , such that when hydraulic piston  24  translates forward within the hydraulic cylinder  22 , the piston rod raises the lift arm  18 .  
         [0024]     In operation of the hydraulic actuator  20 , the user reciprocally pivots handle  16  between an upper position and a lower position. The reciprocal movement of the handle activates drive pump  30  by reciprocally moving drive pump piston  34  within drive pump cylinder  32 . During an upward pivot of the handle  16 , drive pump piston  34  retracts from the end of the drive pump cylinder  32 . During the retraction of the drive pump piston  34 , oil flows through suction/discharge valve  40  and into drive pump cylinder  32 . Preferably, suction/discharge valve  40  is a ball check valve. However, it is also contemplated that suction/discharge valve may be a spring check valve.  
         [0025]     The oil flow into the drive pump cylinder  32  is achieved by the retraction of the drive pump piston  34 , which creates suction in drive pump-suction/discharge valve connection  39 , which seats upper discharge valve ball  48  and unseats lower suction valve ball  44 , which allows oil to flow via oil reservoir connection  42 . During downward movement of handle  16 , the oil in the drive pump  30  is forced through connection  39 , which seats lower suction valve ball  44  and unseats upper discharge valve ball  48 . The oil is then forced into hydraulic cylinder connection  46 , which forces the hydraulic piston  24  forward in the hydraulic cylinder  22 . Any increased pressure in the portion of the hydraulic cylinder  22  forward of hydraulic piston  24  is equalized via equalizing line  70 , which communicates with oil reservoir  36 .  
         [0026]     If the jack  10  is overloaded, such that oil pressure increases beyond acceptable limits during lifting, over-pressure relief valve  50  diverts oil from the drive pump  30  back into the oil reservoir  36 . This over-pressure relief is via high pressure in connection  52 , which unseats spring-closed valve seat  54 , thereby allowing oil to flow through oil reservoir connection  56  back into the oil reservoir  36 . Over-pressure relief valve  50  preferably comprises a spring valve, but it is also contemplated that a ball check valve may be utilized.  
         [0027]     Additionally, if the lift arm  18  is fully extended, by-pass valve  72  prevents over-pressure in the hydraulic cylinder  22 . By-pass valve  72  allows oil to flow through hydraulic piston  24  from the high pressure side of the hydraulic cylinder  22  to the low pressure side of the hydraulic cylinder  22 . This oil flow is triggered by by-pass rod  74  contacting an interior end wall of the hydraulic cylinder  22 , which opens the by-pass valve  72 .  
         [0028]     To lower the lift arm  18 , any oil release system known in the art can be utilized without deviating from the scope of the present invention. In a preferred embodiment, release valve  49  is actuated, such that oil flows from behind the hydraulic piston  24  of the hydraulic cylinder  22 , through connection  46 , through the upper portion of suction/discharge valve  40 , through release valve  49 , and into the oil reservoir  36 . Preferably, the release valve is activated and deactivated by any mechanism known in the art.  
         [0029]     In addition to the hydraulic actuator  20  used to raise lift arm  18 , mechanical actuator  80  may be used to raise the lift arm  18  when the lift arm  18  is under no load or little load. Mechanical actuator  80  preferably comprises ratchet mechanism  82  operably attached to handle  16 , such that downward pivoting of the handle  16  operates ratchet mechanism  80 . Preferably, the mechanical actuator  80  comprises a selector  90  that selectively enables and disables the mechanical actuator  80 . Any type of suitable selector  90  known in the art may be utilized without deviating from the scope of the present invention. In a preferred embodiment, the selector  90  comprises trigger mechanism  92  that selectively engages and disengages pawl  94  with ratchet mechanism  80 .  
         [0030]     Ratchet mechanism  80  is operably connected to lift arm  18  via an articulated linkage. Preferably, the articulated linkage comprises pull bar  84 , pivot link  86 , and push bar  88 . The pull bar  84  extends longitudinally, with one end of the pull bar  84  connected to the ratchet mechanism  82  and the other end of the pull bar  84  connected to the pivot link  86 . One end of the pivot link  86  is connected to the pull bar  84 , the other end of the pivot link  86  being connected to the push bar  88 . It should be understood that the connections among the pull bar  84 , the pivot link  86 , and the push bar  88  are preferably rotatable, such that the angles formed between the pull bar  84  and pivot link  86 , and between the pivot link  86  and push bar  88 , can vary during actuation of the mechanical linkage.  
         [0031]     The push bar  88  is operably connected to the lift arm  18  at a point offset from the pivot point of the lift arm  18 , such that actuation of the push bar  88  raises the lift arm  18 . Preferably, the push bar  88  is connected to the lift arm at a position coaxial to the connector pin  29 . More preferably, the push bar  88  is connected to lift arm  18  via connector pin  29 , which also connects the hydraulic piston rod  26  to the lift arm  18 .  
         [0032]     When the mechanical actuation is used to raise the lift arm  18 , sub-atmospheric pressure, or vacuum, will tend to form in the hydraulic cylinder  22  behind the hydraulic piston  24 . To overcome this problem, a preferred embodiment of the present invention comprises an oil vacuum relief, which in a preferred embodiment comprises oil vacuum relief valve  60 . The oil vacuum relief valve  60  has a connection  62  to the oil reservoir  36 , a valve ball  64 , and a connection  66  to the hydraulic cylinder. When vacuum begins to form in the hydraulic cylinder  22 , the decreased pressure from connection  62  causes valve ball  64  to unseat, which allows oil to flow from the oil reservoir  36 , through connection  62 , through oil vacuum relief valve  60 , through connection  66 , and into the hydraulic cylinder  22 . The vacuum relief allows the lift arm to be fully raised under no load via the mechanical actuation  80 .  
         [0033]     The forgoing disclosure is illustrative of the present invention and is not to be construed as limiting thereof. Although one or more embodiments of the invention have been described, persons of ordinary skill in the art will readily appreciate that numerous modifications could be made without departing from the scope and spirit of the disclosed invention. As such, it should be understood that all such modifications are intended to be included within the scope of this invention. The written description and drawings illustrate the present invention and are not to be construed as limited to the specific embodiments disclosed.