Abstract:
The invention relates to a safety protection device to prevent a lifting mechanism of a jack from completely retracting in the case of a mechanical failure in the lifting mechanism or inadvertent operator error in prematurely releasing the lifting mechanism. The invention also relates to a safety device release mechanism allowing the operator to disengage the safety mechanism, wherein the release mechanism is preferably mountable in a location suitably remote from the lifting mechanism, for example, the release mechanism may be detachably mounted on the handle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 60/881,408, filed Jan. 19, 2007, the entirety of which is hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to a hydraulic jack having a locking mechanism. 
       BACKGROUND 
       [0003]    Various hydraulic floor jacks are known in the art and their use has become very common. However, all hydraulic systems are subject to failure or inadvertent release resulting in an undesirable, and potentially very dangerous, retracting of the lift element. As a result, people should not work under a vehicle or other lifted weight which is supported solely by a floor jack. Nevertheless, people frequently do work under vehicles held aloft solely by a floor jack. Therefore, it is highly desirable to prevent such floor jacks from retracting while in a raised position. 
         [0004]    Examples of hydraulic floor jacks may be found in U.S. Pat. Nos. 1,767,124; 1,784,116; 1,978,451; 2,629,583; and 4,473,213. 
         [0005]    Typically, the hydraulic pump of a floor or service jack is actuated by a handle pivotably connected to the main body of the jack. Typically, such a handle is relatively long and provides a good lever arm for actuating the hydraulic pump and thereby actuating the lifting mechanism of the jack. It would be beneficial to position a safety release mechanism on the distal end of such a handle so as to facilitate release of the safety mechanism and retraction of the jack without the need to approach dangerously close to the lifted object. 
         [0006]    U.S. Pat. No. 5,618,029 (the &#39;029 patent) discloses a jack safety device utilizing a safety hook and a hook-up means. However, this safety device suffers from the fact that the safety hook may not be sufficiently engaged to the hook up means at the time of a failure and would thereafter likely be ineffective in preventing complete retraction of the lifting means. For example, the hook and hook-up means of the &#39;029 patent are both pivotally mounted at opposing ends, thereby causing the hook and/or hook-up to be at a non-optimal angle relative to one another for engagement. In addition, the hook and/or hook-up will drag on the ground beneath the jack interfering with the operators ability to position or move the jack. In contrast, the present invention utilizes a rigidly mounted pawl and ratchet system that will not contact the ground and is structured such that during a failure the locking means is more actively engaged. 
         [0007]    U.S. Pat. No. 5,878,996 (the &#39;996 patent) discloses a lever mechanism for disengaging the safety device of the &#39;029 patent wherein the safety device is described as a pawl pivotably connected to the lift arm and a ratchet fastened at the front end of the main body. In both the &#39;029 and &#39;996 patents the distal end of the disengagement mechanism is located at the back end of the main body. Thus, when the jack is used to lift an object from a position located reasonably far from the periphery of the object, the operator will be required to approach dangerously close to the raised object to disengage the locking mechanism. Furthermore, having the pawl pivotably connected to the lift arm may result in the force vector on the pawl being exerted at an undesirable angle relative to the ratchet or hook up means, which would result in a decreased force in the locking direction. More particularly, the pawl is connected to the lift arm such that the pawl connection point rises with the lift arm, which increases the angle of the pawl relative to the ratchet, thereby decreasing the locking force. Finally, both the &#39;029 and &#39;966 patents describe a safety device wherein the hook or pawl is attached to the lift arm of the floor jack and the hook-up means or ratchet is connected to the front axle, thus creating a complex interaction between the length of the pawl, the length of the ratchet, the location and configuration of the front axle, and the travel distance of the hydraulic piston acting upon the lift arm. 
         [0008]    An additional disadvantage of the configuration described in the &#39;029 and &#39;966 patents is that the hook or pawl of the &#39;029 and &#39;966 patents must extend from the lift arm by a distance greater than the travel distance of the hydraulic piston to engage the hook-up means or ratchet. As a result, when the jack is in the fully retracted position the pawl is necessarily positioned closer to the leading end of the jack in an area having less space. Therefore, the safety device of the &#39;029 and &#39;966 patents requires either a thinner, and structurally less sound, ratchet and pawl or a higher profile jack. 
         [0009]    While the prior art discloses safety means for hydraulic jacks, there exists much room for safety improvement with hydraulic floor jacks. 
       SUMMARY OF THE INVENTION 
       [0010]    The invention relates to a safety protection device to prevent a lifting mechanism of a jack from completely retracting in the case of a mechanical failure in the lifting mechanism or inadvertent operator error in prematurely releasing the lifting mechanism. 
         [0011]    The invention also relates to a safety protection device that may be fitted in a floor jack having a low profile or a floor jack lacking a front axle extending across the main body of the jack. 
         [0012]    The invention also relates to a safety device for a jack having a pawl rigidly affixed to a main body of a jack; a ratchet rigidly affixed to a lifting arm of the jack and having a plurality of teeth configured to engage the pawl, wherein raising the lifting arm of the jack causes the ratchet to travel substantially parallel to a main body of the jack and advance past the rigidly affixed pawl as the lifting arm is raised, wherein engagement of the pawl with the teeth of the ratchet positively restricts downward movement of the lifting arm when a lifting force is removed from the lifting arm. 
         [0013]    The invention may optionally have one or more of the following: the pawl may be biased to a ratchet engaging position, the pawl may engage the ratchet at an angle of less than or equal to about 45 degrees, the pawl may be rigidly affixed approximately equidistant between the opposing walls of the main body, the pawl may be within a ratchet and pawl housing, the pawl and/or the ratchet and pawl housing may be rigidly affixed to a main body of the jack by at least one cylindrical metal rod or at least one substantially longitudinal member, the pawl may be biased to a ratchet engaging position by counter weighting the pawl and/or by use of a spring or other elastic element, a linkage connecting the pawl to a remote actuation site, a lever arm in communication with the linkage, a remote actuation site housing, a passive guide system for the linkage system and combinations thereof. 
         [0014]    The invention also relates to a hydraulic floor jack with a safety system, jack comprising: a hydraulic floor jack having at least two lifting arms, a hydraulic lifting system in communication with the at least two lifting arms, a main body comprising two substantially parallel outer walls and having a front end designed to face the object to be lifted and a rear end, and a handle with one end in communication with the hydraulic lifting system and a second end located distal to the main body; the main body having a rigid member extending between the two outer walls near the front end of the jack and wherein the hydraulic lifting system is located at the rear of the main body; a ratchet rigidly affixed to the at least two lifting arms and having a plurality of teeth; a pawl pivotally connected to the main body between the two substantially parallel outer walls, wherein the pawl is configured to actively engage the ratchet as the lifting arms are raised; and a linkage cable connecting the pawl to a housing located on the distal end of the handle. 
         [0015]    The invention also relates to a safety device release mechanism allowing the operator to facilitate release of the safety device and retraction of the lifting mechanism, wherein the release mechanism is preferably mountable in a location suitably remote from the lifting mechanism. In an exemplary embodiment the invention relates to a release mechanism mountable on a portion of the handle distal from the lifting mechanism, thereby allowing the operator of the jack to release the safety device at a safe distance from the jack. Optionally, the release mechanism may be detachably mounted on the handle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a perspective view in partial cutaway of an exemplary embodiment of the present invention. 
           [0017]      FIG. 2A  is a perspective view in partial cutaway of an exemplary embodiment of the present invention illustrating a cross-bar  11  means for attaching the ratchet and pawl housing  8  to the main body  1  of the jack. 
           [0018]      FIG. 2B  is a perspective view in partial cutaway of an exemplary embodiment of the present invention illustrating a rigid planer plate  11  means for attaching the ratchet and pawl housing  8  to the main body  1 . 
           [0019]      FIG. 3  is a schematical representation of the ratchet  6 , pawl  7 , and ratchet and pawl housing  8 , along with the release mechanism  16 . 
           [0020]      FIG. 4  is a side view of a ratchet  6  adapted for installation in a pre-assembled jack. 
           [0021]      FIG. 5  is a side view of an exemplary embodiment of the present invention. 
           [0022]      FIG. 6  is a perspective view of an exemplary embodiment of the present invention. 
           [0023]      FIG. 7  is a bottom view of an exemplary embodiment of the present invention showing the underside of the jack and a method of connecting the locking mechanism or pawl to a substantially longitudinal member connected to the bottom surface of the outer walls of the main body of the jack. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    By way of example, the locking mechanism and release mechanism are described in view of a hydraulic floor or service jack, however, as will be recognized in view of the present specification, the present device may be adapted to other types of jacks having a lifting arm or lever as a component of the lifting mechanism. 
         [0025]    Referring to  FIG. 1 , the present jack comprises a main body  10 , a holding mechanism  20  having a pair of lifting arms  30  connected to the main body  10 , with the top end of the holding mechanism  20  having a holding portion  40  for lifting an object, and a lifting mechanism  50  for driving the lifting arms  30  upwardly about a pivot point  60  with the holding portion  40  supporting the object being lifted (for example, see, U.S. Pat. No. 4,289,299). 
         [0026]    In the exemplary embodiment illustrated in  FIG. 1 , the present safety device comprises a ratchet  64  rigidly connected to a bar  68  on the end of the ram  72 , where the bar  68  is then connected to the lifting arms  30  (not shown). In this particular configuration, the bar  68  transfers the force and motion of the ram  72  to the lifting arms  30 , and comprises part of the lifting mechanism  50 . In  FIG. 1  a pawl  76  is illustrated inside a ratchet and pawl housing  80 , which is rigidly connected to the main body  10 , wherein raising the lifting arms  30  (i.e., extending the ram  72 ) drives the ratchet  64  past the pawl  76 . The engagement of the pawl  76  with the ratchet  64  then prevents retraction of the lifting arms  30  and/or lifting mechanism  50  upon failure of the lifting mechanism  50  or inadvertent release of the pressure in lifting mechanism  50 . To release the safety mechanism (ratchet  64  and pawl  76 ), the operator manually disengages the pawl  76  from the ratchet  64 . 
         [0027]    Optimally the pawl  76  is connected to the main body  10  at a point proximal to the maximum extension point of the bar  68  and/or ram  72  of the lifting mechanism  50 . In this position the pawl  76  does not restrict the motion of the lifting arms  30 . In addition, the length of the ratchet  64  may be configured such that the ratchet  64  does not limit the maximum extension point of the bar  68  and/or ram  72 . 
         [0028]    While the jack illustrated in  FIG. 1  uses a bar  68  to transmit a lifting force to the lifting arms  30 , this is only one configuration commonly used in floor jacks. For example, U.S. Pat. Nos. 3,181,836 and 5,201,494 illustrate other configurations. In another exemplary embodiment, the ratchet  64  is connected directly or indirectly to the ram  72  of the lifting mechanism, so as to prevent retraction of the lifting arms  30 . 
         [0029]    The jack illustrated in  FIG. 1  has a main body  10  that is made up of two opposing walls and an axle between the two opposing walls. 
         [0030]    In an exemplary embodiment, illustrated in  FIG. 1 , the pawl  76  is rotatably connected to a cross-brace  84  and thereby connected to the main body  10 . Since the pawl  76  is held in a fixed position relative to the main body  10 , retraction of the ratchet  64  is prevented by the pawl  76  and the lift arms  30  cannot be lowered without disengaging the pawl  76  from the ratchet  64 .  FIGS. 2A and 2B  illustrate other exemplary embodiments wherein the ratchet and pawl housing  80  is connected to the main body  10  by other means. For example, in  FIG. 2A  the ratchet and pawl housing  80  is connected to the main body  10  by way of a cross-brace  84  made up of one or more ridged members. In  FIG. 2A  the cross-braces  84 ′ connect to the ratchet an pawl housing  80  at a location other than the pivotal connection point between the ratchet and pawl housing  80  and pawl  76 . In  FIG. 2B  the cross-brace  84 ″ comprises a substantially longitudinal planer member attached to opposing sides of the main body  10  and having the ratchet and pawl housing attached to the cross-member at a point approximately equidistant from the opposing sides of the main body. In an exemplary embodiment, the cross-brace  84 ″ and ratchet and pawl housing  80  may comprise an integral structure connecting the pawl  76  to the main body  10  and allowing the ratchet  64  to slide over the cross-brace  84 ″, while engaging the pawl  76 , thereby helping to support the ratchet  64 . Thus, the cross-brace  84 ,  84 ′,  84 ″ may connect the pawl  76  to the main body  10  by use of a substantially longitudinal planer member (e.g.,  FIG. 2B ), at least one rigid cylindrical member (e.g.,  FIG. 1 ), at least two rigid cylindrical members (e.g.,  FIG. 2A ), a plurality of rigid members, or a combination thereof, and the cross-brace  84 ,  84 ′,  84 ″ may connect to the main body  10  by contacting the inner walls of the opposing sides of the main body  10  or on the bottom of the opposing sides of the main body  10 . The purpose of the cross-brace  84  is to hold the pawl  76  and/or the ratchet and pawl housing  80  in a stationary position relative to the main body  10  regardless of whether the lifting arms  30  are raised or lowered. By holding the pawl  76  stationary and moving the ratchet  64  substantially parallel to the direction of the main body  10 , the height of the locking system can be decreased and the pawl  76  and ratchet  64  can be maintained in an actively engaging position throughout the lifting motion and movement of the lifting arms  30 . The invention also allows for the mounting of a pawl  76 , or a ratchet and pawl housing  80 , to the main body  10  at a position vertically lower than the position of the ratchet  64 , thereby allowing more room within the main body  10  for retraction of the lifting arms  30 . For example, the ratchet and pawl housing  80  and ratchet  64  shown in  FIG. 2A  may be inverted such that the ratchet and pawl housing  80  is below the ratchet  76 . The pawl  76  is preferably elastically encouraged in a ratchet  76  engaging direction or into a ratchet engaged position. 
         [0031]      FIG. 3  provides a cross-sectional view of an exemplary ratchet and pawl housing  80  wherein the ratchet and pawl housing  80  optionally comprises a rigid member  88  or other means for restraining rearward travel of the pawl  76 , thereby preventing retraction of the ratchet  64  and consequently the lifting arms  30 . In an exemplary embodiment, the locking force of the ratchet  64  on the pawl  76  may travel substantially along the pawl  76 , which is connected to the main body  10 , thereby decreasing the profile of the safety device and allowing it to be adapted to low profile jacks. In this configuration the pawl  76  illustrated in  FIG. 3A  engages teeth  65  on the ratchet  64  at an angle ø less than or equal to about 45 degrees, less than or equal to about 40 degrees, less than or equal to about 35 degrees, less than or equal to about 30 degrees, less than or equal to about 25 degrees. In another exemplary embodiment, the ratchet and pawl housing  80  is less than about 4 inches tall, less than about 3.5 inches tall, less than about 3 inches tall, less than about 2.5 inches tall, less than about 2 inches tall, less than about 1.5 inches tall. While  FIG. 3  illustrates a rigid member  88  as one possible means for achieving a maximal rearward travel position for the pawl  76 , other means are known in the art. In addition, the invention allows for the pawl  76  to be positioned such that it engages the ratchet  64  at a low angle ø such that the restraining force along the pawl  76  is substantially parallel to the pawl  76 , thereby increasing the structural soundness of the invention and providing for a lower profile jack. In addition, the pawl  76  of the present invention may optionally be placed under tension, for example, by means of an elastically reciprocating member  92 , such that the pawl  76  actively engages the ratchet  64 . 
         [0032]    While the ratchet and pawl housing  80  in  FIGS. 1 ,  2 , and  3  are illustrated in the form of a ratchet and pawl housing  80  having at least four wall portions, the ratchet  64  and/or pawl  76  need not be in a ratchet and pawl housing  80  and any configuration of a ratchet and pawl housing  80  may be adapted to the invention, so long as the ratchet  64  and pawl  76  prevent retraction of the lifting mechanism  50  and/or lifting arms  30 . 
         [0033]      FIG. 3  also illustrates a elastically reciprocating member  92 , or spring, that holds the pawl  76  in a ratchet engaging position, whereas linkage  96  is connected to the pawl  76 , either directly or indirectly, and is used to move the pawl  76  into a ratchet releasing position by moving the pawl  76  in the direction of the arrow. 
         [0034]    In the exemplary embodiment of  FIG. 3 , the pawl  76  is biased toward an engaging position by an elastically reciprocating member  92 , e.g., a resilient spring, and is moved to a release position by a linkage  96  adapted to overcome the elastically reciprocating member  92  bias and move the pawl  76  to a release position under manual actuation at a location remote from the pawl  76 . In particular, the invention allows a remote actuation site  100  to be situated on the handle  104  of the jack. In this embodiment the jack operator may disengage the pawl  76  at an acceptable distance from the main body  10  of the jack. 
         [0035]    In another exemplary embodiment, the remote actuation site  100  comprises a housing  109  and a release lever assembly  108  connected to the linkage  96 , mounted on the handle of the jack  104  and configured to actuate the linkage  96 , e.g., a flexible cable, such as a steel wire, thereby moving the pawl  76  to a release position. When the release lever assembly  108  is moved to the locking position, the elastically reciprocating member  92  returns the pawl  76  to an engagement position. As will now be apparent, the remote actuation site  100  may be mounted or mountable at any desired position on the handle  104 , preferably at or near the distal end of the handle  104 . Optionally, the remote actuation site  100  may be detachably mounted on the handle  104  of the jack. While the remote actuation site  100  is illustrated as a release lever assembly  108 , any suitable means of actuating the linkage  96  may be used, including, but not limited to, a pull cable system wherein the linkage  96  terminates in a handle, a lever where the pawl is biased to a ratchet engaging position and squeezing the lever moves the pawl to a ratchet releasing position (e.g., similar to those used on a motorcycle activate the clutch or brakes), or other mechanisms known in the art. 
         [0036]    In the exemplary embodiment of  FIG. 4 , the ratchet is adapted to be rigidly connected to the bar  68  ( FIG. 1 ) in a pre-assembled jack. For example, a proximal end  112  of a ratchet  64  is configured to have a channel  116  capable of rigidly engaging the bar  68  and/or ram  72 . Optionally, a tensioning means  120  may be present so as to prevent rotation of the ratchet  64  when mounted on the bar  68 . In another exemplary embodiment, the ratchet and pawl housing  80  is configured to replace a rigid member mounted substantially perpendicular to the two walls of the main body  10 . For example, the ends of cross-brace  84  (e.g.,  FIGS. 1 and 2A ) connected to the ratchet and pawl housing  80  may be threaded and secured to the main body  10  by way of a nut or other threaded locking means. Thus, the invention provides a kit adapted to add a locking system to a pre-assembled jack, wherein the kit may optionally include a ratchet  64 , a pawl  76 , a linkage  96 , and a remote actuation site  100 , optionally including a release lever assembly  108  configured to be secured to the handle  104  of the jack. 
         [0037]    In another exemplary embodiment, the pawl  76  is configured such that it provides a low profile within the main body  10  of the jack. In another exemplary embodiment, the pawl  76  is configured such that the locking force of the ratchet  64  and pawl  76  is transferred substantially parallel to the direction of the pawl  76 , thereby decreasing the profile of the safety device and placing less shear or breakage pressure on the pawl  76 . 
         [0038]      FIGS. 5 ,  6  and  7  show an exemplary embodiment of the invention. In this embodiment, the ratchet  64  is welded to the bar  68 , and the ratchet and pawl housing  80 , including the ratchet  76 , is connected to the main body  10  by means of at least one cross-member  84 . The linkage  96  is connected to the pawl  76 , for example by way of a rigid member in communication with the pawl  76 , such that the linkage  96  can disengage the pawl  76  from the ratchet  64 , then allow the pawl  76  to return to an engaging position when desired. The linkage  96  may include any number of guide paths, such as a port (e.g., eyelet in  FIG. 5 ) or a wheel or groove (e.g.,  FIGS. 6 and 7 ) to allow manual release of the safety device at a desirable distance from the jack. 
         [0039]    All references, including publications, patents, and patent applications, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
         [0040]    While this invention has been described in certain embodiments, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.