Abstract:
The load dependent, variable displacement, at least three-shift hydraulic mechanism includes a hydraulic device disposed at the front side of a valve block and adapted to move a ram piston oriented such as to raise weight, the hydraulic device defining an oil accumulation chamber, a rapid-lifting oil chamber for rapid extension of the ram piston under no-load conditions, and a high-pressure oil chamber for lifting the ram piston oriented to raise weights, a pump piston apparatus disposed at the back side of the valve block and defining a front working chamber and a rear oil accumulation chamber, and oil passages so arranged that hydraulic oil can be supplied from the oil accumulation chamber and the rear oil accumulation chamber to the front working chamber and then to the rapid-lifting oil chamber or the high-pressure oil chamber to extend the ram piston.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This is a CIP application of Ser. No. 10/667,660, filed Sep. 23, 2003, entitled “THREE-SHIFT LIFTING MECHANISM FOR JACK OR THE LIKE”. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     (a) Field of the Invention  
         [0003]     The present invention relates to lifting mechanisms whose load engaging member is adapted to raise weights and, more particularly, to a load dependant, variable displacement jacking mechanism providing at least 3 shifts in performance characteristic relating to the effort expended by the operator and how quickly the lift mechanism and/or the load is raised. Each of the 3 performance characteristics form an operator felt response to the act of raising the lift arm and the load. 
        the first shift/response is one of minimal handle pumping effort as the operator raises a substantially unloaded lifting member quickly to contact the load;     the second shift/response is one of greater than minimal pumping effort as the user raises a considerably less than rated capacity load at a slightly slower raising speed, but significantly more rapid than if the load were rated capacity;     the third shift/response is one of minimal operator effort to raise a significantly greater load but at slower raising speed than the previous response.        
 
         [0007]     (b) Description of the Prior Art  
         [0008]     A lifting mechanism using a conventional hydraulic device for use in a vehicle jack or the like is generally comprised of a valve block containing check valves and passages communicating to a ram piston apparatus and a pump piston apparatus. The pump piston is actuated by a means to suck in hydraulic oil and then to pump hydraulic oil through passages and valving into a lifting tube, causing the ram piston to extend, thereby acting upon the lifting mechanism, causing it to rise. This device has limitations due to the felt response of the operator to the pumping action of the actuator means, i.e. a single slow raising speed whether the lifting mechanism is loaded or unloaded so that the user employs much effort to repeatedly reciprocate the pump piston and the operator expends much actuator pumping effort when the lifting mechanism finally contacts the load. There are known, dual-speed lifting mechanisms that enable the ram piston apparatus to engage the load quickly from a fully retracted lift mechanism position and then continued pumping results in raising the load at a slow speed. However, these dual speed mechanisms have no means of enabling the operator to raise substantially lesser that rated capacity loads quickly, promoting both poor lift performance and operator fatigue. Therefore, it is desirable to provide three stages of felt response in order to eliminate the drawbacks of the conventional lifting mechanism.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a load dependant, variable displacement mechanism which provides at least three stages of lift performance and felt response to same; the first felt response is one of minimal handle pumping effort as the operator raises a substantially unloaded lifting member quickly to contact the load; the second felt response is one of greater than minimal pumping effort as the user raises a considerably less than rated capacity load at a slightly slower raising speed, but significantly more rapid than a load representing rated capacity; the third felt response is one of minimal operator effort to raise a significantly greater load but at a slower raising speed than the previous responses.  
         [0010]     To achieve this and other objects of the present invention, the three-stage lift performance lifting mechanism comprises a hydraulic device comprising a cylindrical casing, a barrel, a ram piston tube, a small tube moveably oriented substantially within the ram piston tube, the casing being a double open end member axially inserted into the inside of the casing and defining within the casing an oil reservoir chamber in between the barrel and the casing, the ram piston tube having an opening and axially mounted in the barrel and forwardly extended out of the casing and adapted to raise the lifting mechanism, the ram piston tube having an axially extending center hole to a rear open side thereof, a piston ring disposed at the periphery thereof near the rear open side and pressed on an inside wall of the barrel, and a high-pressure oil chamber defined within the barrel behind the piston ring, the small tube moveably oriented substantially within the ram piston tube being a double open sided tube inserted into the axial center hole inside the ram piston tube and defining therein a rapid-lifting oil chamber; a pump piston adapted to pump hydraulic oil into the hydraulic device to extend the ram piston, a pump piston comprising a housing and a plunger axially slidably mounted in the housing, the housing being a hollow cylindrical member having at least one oil hole positioned through the periphery thereof in communication with the inside space thereof, the plunger comprising a piston of relatively bigger diameter disposed at the front side inside the housing and a piston rod of relatively smaller diameter disposed at a rear side and extending out of the housing, said piston having a plurality of annular flanges extended around the periphery thereof and pressed on an inside wall of the housing and defining the inside space of the housing into a front working chamber and a rear oil accumulator chamber, the piston having an oil hole axially backwardly extended from the center of a front side thereof then directed sideways to the periphery thereof in communication between the front working chamber and the rear oil accumulator chamber, and a one-way valve means comprising a spring member, a steel ball, a ball seat and mounted in the oil hole of the piston to control one-way flow of hydraulic oil from the rear oil accumulator chamber to the front working chamber; and a valve block adapted to accommodate the hydraulic device and the piston pump, the valve block comprising a front coupling flange fitted into a rear open side of the cylindrical casing, a recessed portion disposed at the center of the front coupling flange and adapted to accommodate the barrel and the small center tube, a receiving hole adapted to accommodate the piston pump and to block the front working chamber, 
        a first oil passage extended from the oil accumulation chamber to the front working chamber,     a second oil passage extended from the front working chamber to the high-pressure oil chamber and the rapid-lifting oil chamber,     a third oil passage extended from the oil accumulation chamber to the high-pressure oil chamber,     a fourth oil passage extended from the oil accumulation chamber to the rear oil accumulation chamber,     a fifth oil passage shunted from the second oil passage and extended to the rear buffer chamber,     a sixth oil passage extended from the rapid lifting oil chamber to the oil accumulation chamber,     and a seventh oil passage extended from the high-pressure oil chamber to the oil accumulation chamber.        
 
         [0018]     By means of the aforesaid arrangement, hydraulic oil is supplied from the rear oil accumulation chamber and the oil reservoir chamber to the front working chamber for pumping to the rapid-lifting oil chamber producing performance characteristics which are load dependent; one of minimal handle pumping effort as the operator raises a substantially unloaded lifting member quickly to contact the load; 
        OR for pumping to the rapid-lifting oil chamber and to the high-pressure oil chamber through one of at least 3 preset pressure relief valves. An additional benefit is that during the pumping of hydraulic oil into the high-pressure oil chamber through one or more preset pressure relief valves, hydraulic oil is simultaneously guided into the rear oil accumulation chamber of the pump piston for enabling the front working chamber to suck in hydraulic oil from the rear oil accumulation chamber and the oil accumulation chamber enabling a more efficient pumping action.       
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a sectional view of a 3 stage hydraulic lifting mechanism according to the present invention.  
         [0021]      FIG. 2  is a block diagram showing the linking of the oil chambers and oil passages according to the present invention.  
         [0022]      FIG. 3  is a sectional view of the valve block according to the present invention.  
         [0023]      FIG. 4  is a top view of the valve block according to the present invention.  
         [0024]      FIG. 5  is a sectional view of the third oil passage according to the present invention.  
         [0025]      FIG. 6  is a sectional view of the fourth oil passage according to the present invention.  
         [0026]      FIG. 7  is a sectional view of the pump piston apparatus according to the present invention.  
         [0027]      FIG. 8  is a schematic drawing showing the action of the pump piston apparatus according to the present invention (I).  
         [0028]      FIG. 9  is a schematic drawing showing the action of the pump piston apparatus according to the present invention (II).  
         [0029]      FIG. 10  is a schematic drawing showing hydraulic oil pumped into the second oil passage according to the present invention.  
         [0030]      FIG. 11  is a schematic drawing showing hydraulic oil pumped into the rapid-lifting oil chamber according to the present invention.  
         [0031]      FIG. 12  is a schematic drawing showing hydraulic oil supplied from the oil accumulation chamber to the high-pressure oil chamber according to the present invention.  
         [0032]      FIG. 13  is a schematic drawing showing hydraulic oil supplied from the oil accumulation chamber to the rear oil accumulation chamber according to the present invention.  
         [0033]      FIG. 14  is a schematic drawing showing hydraulic oil pumped into the second oil passage according to the present invention.  
         [0034]      FIG. 15  is a schematic drawing showing hydraulic oil pumped into the high-pressure oil chamber according to the present invention.  
         [0035]      FIG. 16  is a schematic drawing showing hydraulic oil flow into the rear oil accumulation chamber according to the present invention.  
         [0036]      FIG. 17  (does not appear to be right) is a schematic drawing showing hydraulic oil shunted into the rear oil accumulation chamber upon an overload at the lifting tube according to the present invention.  
         [0037]      FIG. 18  (does not appear at all) shows the three-stage lifting mechanism used in a jack according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]     Referring to FIGS.  1 ˜ 3 , a load dependent, variable displacement, at least three-shift lifting mechanism in accordance with the present invention can be installed in a jack (see  FIG. 18 ) or used directly to lift weights, comprising a hydraulic device  1 , a pump piston apparatus  2 , and a valve block  3 . The hydraulic device  1  (see  FIG. 1 ) comprises a cylindrical casing  11 , a barrel  12 , a ram piston  13 , and a small center tube  14 . The casing  11  is a double open end cylinder having the front side mounted to an oil seal ring containing member  111  and the periphery provided with a stopper  112 . The barrel  12  is a double open end member axially inserted into the inside of the casing  11 , having the front open side in communication with the casing  11  via the oil seal ring within  111 . An oil accumulation chamber (reservoir) A is defined between the casing  11  and the barrel  12 . The lifting tube  13  is a one open side tube adapted to engage the bearing pan  101  of the jack  100 , having front coupling rod  131  axially forwardly extended from the front closed side and coupled to the bearing pan  101  of the jack  100 , an axial center hole  132  axially extended to the rear open side, a piston ring  133  disposed at the periphery near the rear open side, and a locating device  134  disposed at the periphery adjacent to the piston ring  133 . The lifting tube  13  is axially mounted in the barrel  12 , keeping the front coupling rod  131  disposed outside the oil seal ring within  111  and the piston ring  133  pressed on the inner diameter of the barrel  12 . Therefore, a high-pressure oil chamber B is defined within the barrel  12  behind the piston ring  133 . Hydraulic oil can be pumped into the high-pressure oil chamber B to drive the lifting tube to lift the load.  
         [0039]     The small center tube  14  is a double open side tube inserted into the axial center hole  132  inside the lifting tube  13 , defining therein a rapid-lifting oil chamber C into which hydraulic oil is pumped to lift the lifting tube  13  rapidly. The pump piston  2  (see  FIGS. 1 and 7 ) is provided for operation by the user to pump hydraulic oil into the hydraulic device  1  to extend the lifting tube. The pump piston comprising a housing  21  and a plunger  22 . The housing  21  is a hollow cylindrical member having a front oil chamber  211 , a plunger hole  212  in communication with the bottom side of the front oil chamber  211 , and a plurality of oil holes  213  cut through the periphery in communication with the front oil chamber  211 . The plunger  22  is axially slidably mounted in the housing  21 , having a piston  221  of relatively bigger diameter disposed at the front side inside the oil chamber  211  and a piston rod  222  of relatively smaller diameter disposed at the rear side and extended out of the rear side of the housing  21 . The piston  221  has a plurality of annular flanges  223  extended around the periphery and provided on the peripheral wall of the oil chamber (i.e., the inner diameter of the housing  21 ). Therefore the piston  221  divides the oil chamber  211  into a front working chamber D and a rear oil accumulation chamber E. Further, the piston  221  has an oil hole  224  axially backwardly extended from the center of the front side, then turned sideways to the periphery in communication between the front working chamber D and the rear working chamber E, a one-way valve formed of a spring member  226  and a steel ball  225  and mounted in the oil hole  224  to control one-way flowing of hydraulic oil from the rear working chamber E to the front working chamber D.  
         [0040]     The valve block  3  (see  FIGS. 1 and 2 ) is mounted inside the jack  100  and adapted to accommodate the hydraulic device  1  and the piston pump  2  and to link the oil accumulation chamber A, the high-pressure oil chamber B, the rapid-lifting oil chamber C, the front working chamber D, rear working chamber E. The valve block  3  comprises a front coupling flange  31  fitted into the rear open side of the cylindrical casing  11 , a recessed portion  32  disposed at the center of the front coupling flange  31 , which receives the barrel  11  and the small center tube  14 , a rear receiving hole  33 , which accommodates the pump piston apparatus  2  and blocks the front working chamber D, a first oil passage F extended from the oil accumulation chamber A to the front working chamber D, a second oil passage G extended from the front working chamber D to the high-pressure oil chamber B and the rapid-lifting oil chamber C, a third oil passage H extended from the oil accumulation chamber A to the high-pressure oil chamber B, a fourth oil passage I extended from the oil accumulation chamber A to the rear working chamber E, a fifth oil passage J shunted from the second oil passage G and extended to the rear working chamber E, a sixth oil passage K extended from the rapid-lifting oil chamber C to the oil accumulation chamber A, and a seventh oil passage L extended from the high-pressure oil chamber B to the oil accumulation chamber A.  
         [0041]     As indicated above, the first oil passage F extends from the oil accumulation chamber A to the front working chamber D. As shown in  FIGS. 1 and 3 , the first oil passage F is formed of a first transverse oil hole  341 , an oil hole  342  extended from the bottom end of the first transverse oil hole  341  to the rear receiving hole  33  (i.e., the front working chamber D of the housing  21 ), a stepped first longitudinal oil hole  343  extended across the first transverse oil hole  341 , an oil hole  344  extended from the bottom end of the stepped first longitudinal oil hole  343  to the front side of the valve block  3  in communication with the oil accumulation chamber A of the barrel  11 , and a one-way valve formed of a steel ball  345  mounted in the first stepped longitudinal oil hole  343  and stopped between the oil hole  344  and the oil hole  342 . Upon upstroke of the pump piston  2 , hydraulic oil is pumped out of the oil accumulation chamber A to push the steel ball  345  out of position and then to pass to the front working chamber D.  
         [0042]     As indicated above, the second oil passage G extends from the front working chamber D to the high-pressure oil chamber B and the rapid-lifting oil chamber C. As shown in  FIGS. 1, 3 , and  4 , the second oil passage G is formed of a second transverse oil hole  343 , an oil hole  352  extended from the second transverse oil hole  351  to the rapid-lifting oil chamber C (see  FIG. 1 ), a second longitudinal oil hole  353  extended across the second transverse oil hole  353  and works as a one-way valve means, a pressure regulator  355  disposed at the top end of the second longitudinal oil hole  353 , an oil hole (not shown) extended from the second longitudinal oil hole  353  to the high-pressure oil chamber B, a steel ball  356  mounted in the first longitudinal oil hole  343  between the first transverse oil hole  341  and the second transverse oil hole  351 . Upon down (compression) stroke of the pump piston apparatus  2 , hydraulic oil passes out of the front working chamber D to push open the steel ball  356  and to pass to the inside of the rapid-lifting oil chamber C, or to further push open the steel ball  354  and the pressure regulator  355  and then to pass to the inside of the high-pressure oil chamber B, and therefore the lifting tube  13  and lifting mechanism is rapidly moved to the weights (1st Stage), or forced to lift the weights (2nd Stage).  
         [0043]     As indicated above, the third oil passage H extends from the oil accumulation chamber A to the high-pressure oil chamber B. As shown in  FIGS. 2 and 5 , the third oil passage H comprises a curved hole  361  extended from the front side of the front coupling flange  31  of the valve block  3  to the recessed portion  32 , a steel ball  362  mounted in the oil hole  361  and worked as a one-way valve means. During rapid extension of the lifting tube (ram piston)  13 , hydraulic oil is supplied from the oil accumulation chamber A to fill up the high-pressure oil chamber B for further pumping by the pump piston apparatus  2  to forcefully extend the lifting tube  13 , thereby raising the weights.  
         [0044]     As indicated above, the fourth oil passage I extends from the oil accumulation chamber A to the rear oil accumulation chamber E. As shown in  FIGS. 2, 4 , and  6 , the fourth oil passage I comprises an oil hole  371  shunted from the first longitudinal oil hole  343  below the steel ball  345 , a third longitudinal oil hole  372  disposed inside the valve block  3  and across the oil hole  371 , an oil hole  373  extended from the third longitudinal oil hole  372  to the rear receiving hole  33 , a steel ball  374  mounted in between the oil hole  372  and the oil hole  373  and working as one-way valve means. Further, by means of the oil holes  213  and the housing  21 , the oil hole  373  is in fluid communication with the rear oil accumulation chamber E. Upon down stroke of the pump piston apparatus  2 , hydraulic oil is sucked from the oil accumulation chamber A into the rear oil accumulation chamber E.  
         [0045]     As indicated above, the fifth oil passage J is shunted from the second oil passage G and extended to the rear oil accumulation chamber E. As shown in FIGS.  2 ˜ 4 , the fifth oil passage J is formed of a fourth longitudinal oil hole  381  in fluid communication with the first transverse oil hole  341 , a steel ball  382  mounted in the fourth longitudinal oil hole  381  and working as a one-way valve means, a pressure regulator  383  mounted in the fourth longitudinal oil hole  381  above the steel ball  382 , an oil hole  384  in fluid communication between the fourth longitudinal oil hole  381  and the third longitudinal oil hole  372 . Upon an overload at the lifting tube  13 , a quantity of hydraulic fluid passes through the fifth oil passage J to the rear oil accumulation chamber E, and a quantity of hydraulic oil pushes open the steel ball  354  and the pressure regulator  355  and then passes to high-pressure oil chamber B to extend the lifting tube  13  more slowly than 1st and 2nd stage and substantially reducing operator pumping effort (third stage).  
         [0046]     As indicated above, the sixth oil passage K extends from the rapid-lifting oil chamber C to the oil accumulation chamber A. As shown in  FIGS. 1 and 2 , the sixth oil passage K is formed of an oil hole  391  disposed at the recessed portion  32  of the valve block  3 , a steel ball  392  mounted in the oil hole  391  and working as one-way valve means for enabling hydraulic oil to pass from the rapid-lifting oil chamber C to the oil accumulation chamber A, a pressure regulator  393  mounted in the oil hole  391  above the steel ball  392 , an oil hole  394  in fluid communication with the oil hole  391 , an oil hole  395  extended from the oil hole  394  to the front side of the front coupling flange  31  in fluid communication with the oil accumulation chamber A. Upon return stroke of the lifting tube  13 , hydraulic oil return from the rapid-lifting oil chamber C to the oil accumulation chamber A.  
         [0047]     As indicated above, the seventh oil passage L extends from the high-pressure oil chamber B to the oil accumulation chamber A (see  FIG. 2 ). The seventh oil passage L is an oil hole having one-way valve means, for example, a steel ball is mounted therein to control the flowing direction of hydraulic oil. Upon return stroke of the lifting tube (ram piston)  13 , hydraulic oil flows backwards from the high-pressure oil chamber B to the oil accumulation chamber A via the seventh oil passage L. As an application example of the present invention, the 3-stage lifting mechanism is used in a jack  100  and operated as follows:  
         [0048]     1. First Stage, i.e., rapid movement of the lifting tube  13  to the weights: The plunger  22  of the pump piston apparatus  2  is lifted (see  FIGS. 8 &amp; 9 ) to draw fluid from the oil accumulation chamber A into the front working chamber D via the first oil passage F (hydraulic oil pushes open the steel ball  345 ), and simultaneously to draw hydraulic oil from the rear oil accumulation chamber E into the front working chamber D via the oil hole  224  and the steel ball  225 , thereafter the plunger  22  of the pump piston apparatus  2  is moved in an opposing direction thereby compressing the hydraulic fluid and moving same out of the front working chamber D into the rapid-lifting oil chamber C through the second oil passage G. Because the lifting tube  13  does not bear any weights at this time, the rapid-lifting oil chamber C which has a relatively smaller cross section is selected to extend the lifting tube  13 , and therefore the lifting tube  13  can be rapidly moved to the bottom side of the weights. During rapid-lifting of the lifting tube  13  as above, the high-pressure oil chamber B becomes a chamber exhibiting negative pressure, therefore hydraulic oil is sucked from the oil accumulation chamber A to the high-pressure oil chamber B via the third oil passage H (see  FIG. 12 ) for further working upon the next downward stroke of the pump piston apparatus plunger  22 . Upon downstroke of the pump piston apparatus plunger  22  to squeeze hydraulic oil out of the front working chamber D, the rear oil accumulation chamber E is in negative pressure status, therefore hydraulic oil is sucked from the oil accumulation chamber A into the rear oil accumulation chamber E via the fourth oil passage I (see  FIG. 13  and  FIG. 16 ) for further quick supply of hydraulic oil to the front working chamber D during the next upstroke of the pump piston apparatus plunger  22 .  
         [0049]     2. Second stage, i.e., the lifting action of the lifting tube  13  to raise substantially lesser than rated capacity weights: Repeating the pumping action of the pump piston apparatus plunger  22  (see  FIGS. 14 and 15 ) to fill up the front working chamber D with hydraulic oil. Because the lifting tube has ceased further extension upon reaching the weights, a downstroke of the pump piston apparatus plunger  22  causes hydraulic oil to pass from the second oil passage G into the high-pressure oil chamber B via the steel ball  354  and the pressure regulator  355 , and therefore the high-pressure oil chamber B which has a relatively greater cross section is used to lift the lifting tube  13  to raise the weights. During the down stroke (compression stroke) of the pump piston apparatus plunger  22  to squeeze hydraulic oil out of the front working chamber D, the rear oil accumulation chamber E is changed to a negative pressure status therefore hydraulic oil is sucked from the oil accumulation chamber A into the rear oil accumulation chamber via the fourth oil passage I (see  FIGS. 13 and 16 ) for further quick supply of hydraulic oil to the front working chamber D during the next upstroke of the pump piston apparatus plunger  22 .  
         [0050]     3. Third stage, i.e., the lifting action of the lifting tube beyond the preset of pressure regulator  355 : Repeating the action of pump piston apparatus plunger  22  (see  FIGS. 16 and 17 ) to fill up the front working chamber D with hydraulic oil. Upon downstroke of plunger  22  after the front working chamber D has been filled with hydraulic oil, hydraulic oil is forced into the high-pressure oil chamber B to extend the lifting tube  13 . If the weight is beyond the preset of pressure regulator  355  at this time, a quantity of hydraulic oil pumped by pump piston apparatus plunger  22  is shunted from the second oil passage G to the fifth oil passage I (see  FIG. 17 ) and then to the rear oil accumulation chamber E in the pump piston apparatus  2  (see  FIG. 16 ), and a quantity of hydraulic oil pushes open the steel ball  354  and the pressure regulator  365  and then to the high-pressure oil chamber B to extend the lifting tube  13  (see  FIG. 17 ) and further raise the weights at a lesser rate of ascent than 2nd stage level and a substantially reduced operator effort. During return stroke of the lifting tube  13  to lower the weights, hydraulic oil passes from the high-pressure oil chamber B and the rapid-lifting oil chamber C to the oil accumulation chamber A via the seventh oil passage L and the sixth oil passage K respectively, enabling the lifting tube  13  to be lowered.  
         [0051]     A prototype of three-stage lifting mechanism has been constructed with the features of FIGS.  1 ˜ 18 . The three-stage lifting mechanism functions to provide all of the features discussed earlier.  
         [0052]     Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except by the appended claims.