Abstract:
A post puller features a lifting member that is slidably disposed on a guide shaft and attachable to a lifting arrangement of a working machine. A pair of movable grippers are pivotally supported on the guide shaft at a fixed position therealong, and a pair of links are pivotally connected between the lifting member and the grippers. With a web or flange of the post received in a space between inner ends of the movable grippers, raising of the lifting member by the working machine lifts the outer ends of the movable grippers via the pair of links, thereby lowering inner ends of the grippers into closer proximity to one another to grip the web or flange of the post between the grippers. With the post gripped in this manner, further raising of the lifting member by the working machine pulls the post from the ground.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to devices and methods for pulling of metal fence posts or the like from the ground, and more particularly to a solution employing pivotal cam-shaped grippers that are actuated by application of an upward pulling force on the post puller by the lifting arrangement of a working machine. 
     BACKGROUND 
     Metal (typically steel) posts or pickets are commonly employed for temporary fencing measures, and most commonly feature a T-shaped, t-shaped, Y-shaped, or star-shaped cross section. In a common temporary fencing setup, a series of posts are driven into the ground at spaced apart positions along the intended fence line, and then wire mesh is strung up between adjacent posts using a series of teeth that are provided on a flange or web of the post. When it becomes desirable to take down or relocate the fence, the mesh is removed and rolled up, and the posts are pulled free of their previously embedded positions in the ground. 
     A number of devices have been previously proposed for the purpose of pulling posts from the ground, including those disclosed in U.S. patents U.S. Pat. No. 1,774,661, U.S. Pat. No. 4,422,621, U.S. Pat. No. 4,721,335, U.S. Pat. No. 5,011,117, U.S. Pat. No. 5,368,277, U.S. Pat. No. 7,059,587, U.S. Pat. No. 7,290,754, U.S. Pat. No. 7,963,051, U.S. Pat. No. 8,608,132 and U.S. Pat. No. 8,453,993; U.S. Patent Application Publications US2007/0183121, US2012/0279737 and US20090028649; and PCT Publication WO2012116405. 
     Of these references, U.S. Pat. No. 1,774,661 and U.S. Pat. No. 8,453,993 employ a cam-based post gripping mechanism that is most comparable to that of the present invention, but rely on manual levers to provide the post gripping and pulling forces required to grip the post and pull it free from the ground. Other references make use of external equipment to provide the lifting and gripping force, but not in a manner compatible with a cam-based gripping mechanism like that employed in the present invention. 
     Applicant has therefore developed a unique solution for actuating post grippers of a post puller using a skid steer, front end loader, excavator, back hoe or other working machine with a powered lifting arrangement. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention there is provided a post puller for pulling a post from a ground embedded position standing upright from a ground surface, the post puller comprising: 
     a lifting member having a coupling point thereon that is configured for attachment to lifting arrangement of a working machine to enable upward lifting of said lifting member by the lifting arrangement of the working machine; 
     a sliding sleeve attached to the lifting member; 
     a guide shaft about which the sliding sleeve is disposed for axial sliding of the sleeve up and down along a longitudinal axis of the guide shaft; 
     a pair of movable grippers pivotally supported on the guide shaft by respective pivotal connections on opposing sides of a central longitudinal plane thereof at a fixed location along the longitudinal axis of the guide shaft, each movable gripper having an inner end with a cam-shaped gripping surface that faces across the central longitudinal plane of the guide shaft toward the cam-shaped gripping surface of the other movable gripper, and an opposing outer end spaced laterally outward to a respective side of the guide shaft, each cam-shaped gripping surface increasing in a radial distance thereof from a pivot axis of the respective pivotal connection in a direction moving upward from an imaginary axis intersecting the pivot axes of the pivotal connections; 
     a pair of links having upper ends pivotally coupled to the lifting member and respective lower ends each pivotally coupled to a respective one of the movable grippers proximate the outer end thereof, whereby raising of the lifting member by the working machine with a web or flange of the post received in a space between the inner ends of the movable grippers lifts the outer ends of the movable grippers via the pair of links, thereby lowering the inner ends of the grippers about the pivot axis and bringing the cam-shaped gripping surfaces into closer proximity to one another to grip the web or flange of the post between the gripping surfaces and pull the post from the embedded position under further raising of the lifting member by the working machine. 
     Preferably there are provided upper and lower braces situated above and below the movable grippers on a same side of the guide post as said movable grippers, each brace defining a slot for receiving the web or flange of the post therein to align the web or flange in the space between the inner ends of the grippers. 
     Preferably there is provided a ledge projecting outward from the guide shaft to a same side thereof at which the movable grippers are disposed for resting of said ledge atop the post during placement of the post puller in an operational position situating the web or flange of the post in the space between the inner ends of the grippers. 
     Preferably the ledge resides at a position above the upper brace. 
     Preferably the lower brace resides below the fixed position of the movable grippers at a further distance therefrom than the upper brace. 
     Preferably there is provided at least one handle attached to the guide shaft. 
     Preferably the at least one handle extends to a side of the guide shaft opposite the movable grippers. 
     Preferably the at least one handle comprises a pair of handles each extending laterally outward from the post to a respective side thereof in opposing directions away from the central longitudinal plane of the guide shaft. 
     Preferably each handle comprises an open grip handle having upper and lower arms attached to the guide shaft at spaced apart positions along the longitudinal axis, a central span joining the upper and lower arms together at a radial distance outward from the guide shaft, and an open space bound between the arms, the central span and the guide shaft for gripping of the handle through said open space. 
     According to a second aspect of the invention, there is provided a method of pulling a post from a ground embedded position standing upright from a ground surface, the method comprising: 
     (a) positioning the post puller according to anyone of claims  1  to  9  in an operating position in which the web or flange of the post is received in the space between the movable grippers; 
     (b) supporting the post puller in the operating position independently of the lifting member thereof such that lifting member and links are gravitationally biased downward to push downwardly on the outer ends of the gripping members and raise the inner ends of the gripping members into an open position maximizing the space between the cam shaped gripping surfaces of the gripping members; 
     (c) pulling upwardly on the lifting member using the lifting arrangement of the working machine, and thereby displacing the sliding sleeve upwardly along the guide shaft and pivoting the movable grippers in a direction moving the cam-shaped gripping surfaces closer together and into frictional engagement with the flange or web received in the space between the gripping surfaces; and 
     (d) with the flange or web frictionally gripped between the gripping surfaces of the movable grippers, pulling the lifting member further upward using the lifting arrangement of the working machine, thereby pulling the post out of the embedded position. 
     Supporting the post puller independently of the lifting member in step (b) preferably comprises seating the post puller atop the post at an upper end thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: 
         FIG. 1  is an elevational front view of a post puller of the present invention in a ready state for acceptance of a web or flange of a post (not shown) between two movable grippers of the puller. 
         FIG. 2  is an elevational front view of the post puller in an actuated state gripping state in which gripping surfaces of the grippers have been brought together for the purpose of gripping the web or flange of the post (not shown) between the grippers. 
         FIG. 3  is an elevational side view of the post puller. 
         FIG. 4  is a rear elevational view of the post puller in the ready state. 
         FIG. 5  is a perspective view of the post puller in the gripping state during use, in which the post puller is lifted by a cable, strap, or line coupled to the lifting arms of a skid steer, front end loader, excavator, back hoe, or other working machine. 
     
    
    
     In the drawings like characters of reference indicate corresponding parts in the different figures. 
     DETAILED DESCRIPTION 
       FIGS. 1 to 4  illustrate a post puller  10  according to one embodiment of the present invention, which is generally made up of a upright guide shaft  12 , a hollow sliding sleeve  14 , a lifting member  16 , a pair of links  18 , a pair of movable grippers  20 , a pair of braces  22 , a resting ledge  28  and a pair of handles  26 . The terms vertical and horizontal are used herein in relation to the illustrated orientation of the post puller shown in the drawings, in which the guide shaft  12  stands vertically upright so as to lie parallel to a vertical fence post when used thereon. However, in actual practice, fence posts will of course not always stand truly vertical, and so the orientation of the tool will likewise deviate from the vertical orientation described and shown. The terms horizontal and vertical are therefore used only to distinguish the components that lie more vertical than horizontal from those that lie more horizontal than vertical. 
     The guide shaft  12  and sliding sleeve  14  are both formed of rectangular metal tubing, and the sliding sleeve  14  has a slightly larger cross-sectional area and is concentrically disposed around the guide shaft  12  for sliding movement upwardly and downwardly therealong in the upright longitudinal direction of the shaft  12 . A resting ledge  28  in the form of a small flat horizontal plate welded or otherwise attached to the shaft extends forwardly therefrom at a distance below the top end of the shaft  12 . The sliding sleeve is disposed around the shaft  12  at the portion thereof residing above this resting ledge  28 . The ledge  28  thus defines a stop that prevents the sleeve  14  from sliding downwardly past the ledge  28 , thereby constraining the sleeve&#39;s range of travel to an upper portion of the guide shaft  12 . 
     The lifting member  16  is a flat plate welded or otherwise attached to the front side of the sliding sleeve  14  in a position residing parallel thereto at a short distance forwardly outward therefrom. A coupling point  30  is provided near the top of the lifting member  16  in the form of a through-hole passing horizontally therethrough. Near two lower corners of the lifting member  16 , the two links  18  are respectively coupled to the front face of the lifting member  16  by respective pivot pins  32  passing horizontally through the lifting member  16  in the same direction as the coupling point through hole  30 . As a result, each link  18  is pivotal about a horizontal pivot axis that passes perpendicularly through the lifting member plate  16 . The links are therefore pivotal within a vertical plane lying parallel to the lifting member plate  16  on the front side thereof opposite the shaft  12 . 
     At an intermediate location along the length of the shaft  12 , a mounting bracket  34  is welded or otherwise attached thereto in a position jutting outwardly from the shaft  12  on at least the front and lateral sides thereof. At a front end of the bracket  34 , each one of the movable grippers  20  is pivotally coupled thereto by a respective pivot pin  36  that passes horizontally through the mounting bracket  34  on a respective side of the shaft  12  in a direction parallel to the pivot pins  32  at the upper ends of the links  18 . A respective cotter pin  38  or other suitable locking secures each of the pivot pins  36  in place by cooperating with the head  36   a  of each pivot pin  36  at the other end thereof to prevent sliding of the pivot pin out of the mounting bracket  34  in either direction. This set of pivot pins  36  cooperates with the mounting bracket  34  affixed on the shaft to pivotally mount the movable grippers  20  on the shaft, and therefore may also be referred to herein as mounting pins  36  in order to better distinguish same over the other pivot pins used elsewhere in the assembled post puller. 
     Yet another pair of pivot pins  36  are used to pivotally connect the movable gripping members  20  to the links  18  that hang downwardly from the lifting member  16 . These pivot pins  36  are also referred to herein as connection pins  40  to better distinguish same over the other pivot pins in the assembled post puller. Each connection pin  40  extends through the respective gripper  20  near the outer end thereof that lies distal to the guide shaft  12 , and lies parallel to the other two sets of pivot pins  32 ,  36 . The mounting pins  36  extend through the movable grippers  36  near the inner ends thereof that reside adjacent to a central longitudinal plane of the shaft  12  on opposite sides of this central longitudinal plane. The inner end of each movable gripper  20  is curved non-concentrically around the axis of the respective mounting pin  36  to create a cam-shape that increases in its radial distance from the mounting pin axis in a direction moving upward from an imaginary horizontal axis that perpendicularly intersects the axes of the mounting pins  36 . An upper portion of the inner end of each gripper  20  is serrated to define a series of gripping teeth, therefore defining a gripping surface  20   a  that faces toward that of the other gripper across the gap or open space left between the inner ends of the grippers. 
     An upper brace  22   a  of the post puller resides at a location below the resting ledge  28  and above the mounting bracket and movable grippers. The brace  22  features a small horizontal plate welded or otherwise attached to the shaft  12  in a position projecting forwardly outward from the front side thereof on the same side of the shaft  12  as the linkage formed by the lifting member  16 , links  18  and grippers  20 . A lower brace  22   b  likewise projects forwardly from the shaft, but at the lower end thereof situated at a distance below the mounting bracket and movable grippers  20 . Each brace  22   a ,  22   b  features a linear slot  42  that cuts into the brace plate from the distal end thereof that lies opposite to the shaft  12 , whereby the remaining intact portions of the brace plate on opposite sides of the slot define a pair of tongs. Beneath the ledge  28 , a pair of side walls  44  depend vertically downward from the ledge  28  toward the upper brace  22   a  on opposite sides of the shaft  12 . In the illustrated embodiment, the resting ledge  28 , upper brace  22   a  and side walls  44  are separately defined by respective plates, but in other embodiments, one or more of these components may be integrally combined into a single piece unit. For example, the resting ledge  28 , upper brace  22   a  and side walls  44  may be integrally defined by a piece of rectangular tubing that is laser-cut or otherwise configured into a suitable shape for mounting to the guide shaft. 
     Completing the structure of the post puller are the pair of handles  26 , each of which is provided in the form of a three-segment bar. Each bar-type handle  26  has a lower arm  26   a  jutting horizontally outward from the shaft  12  at or near the lower end thereof at an oblique angle so as to span laterally and rearwardly away from the shaft  12 . A similar upper arm  26   b  likewise juts horizontally outward from the shaft at an oblique angle matching that of the lower arm  26   a , but farther up the shaft  12 , for example at the same elevation as the upper brace  22   a . A central span  26   c  of each bar-type handle spans vertically between the upper and lower arms  26   a ,  26   b  thereof to complete an open-handle configuration that features an open handle space  46  bound by cooperation of the arms and central span of the handle with the shaft  12 . 
     Having defined the structure of the post puller, attention is now turned to the operation of its grippers. Due to the linkage defined by the pivotal connection of the links  18  between the lifting member  16  and the grippers  20 , raising of the lifting member  16  relative to the shaft  12  pulls the outer ends of the grippers  20  upward about the axes of mounting pins  36 , which causes the inner ends of the grippers  20  to pivot downwardly about the axes of the mounting pins  36 . Due to the cam-shaped configuration of the serrated gripping surfaces  20   a  of the grippers  20 , this causes the gripping surfaces  20   a  to move closer together across the central longitudinal plane of the shaft  12 , thereby reducing the width of the gap or space therebetween.  FIG. 1  shows the post puller in its default ready state, where the weight of the sleeve  14  and attached lifting member gravitationally bias the lifting member  16  into a lowered position seated atop the resting ledge  28 . This gravitational action biases the outer ends of the grippers  20  downwardly about the axes of the mounting pins  36 , which in turn biases the gripping surfaces  20   a  at the inner ends of the grippers upwardly about these axis, and away from one another. Accordingly, in the default state of the post puller, the gap or space between the gripping surfaces  20   a  of the grippers is maximized. 
     With reference to  FIG. 2 , when the lifting member  16  is lifted up relative to the shaft, thereby lifting the sleeve  14  up off of the resting ledge  28 , this lifting action raises the outer ends of the grippers  20  about the axes of the mounting pins  36 , which in turn lowers the inner ends of the grippers about the axes of the mounting pins and thereby forces the serrated gripping surfaces  20   a  at the inner ends of the grippers toward the central longitudinal plane of the shaft, thus moving these gripping surfaces closer together to reduce the width of the gap or space between them. 
     Turning to  FIG. 5 , use of the post puller to remove a post  100  from its embedded position in the ground is now described as follows. A user grips the two handles  26  in his or her hands and uses same to manually lift the post puller to a position raising the resting ledge  28  to a height great than the top end of the post  100 . With the slots  42  in the two braces  22   a ,  22   b  aligned with a web or flange  102  of the post  100 , the post puller is manually displaced in a horizontal direction toward the post from the side thereof to which this web or flange  102  extends, until either the free outer edge of the web or flange bottoms out in the slots of the braces  22   a ,  22   b  or the distal ends of the prongs of the braces  22   a ,  22   b  are brought into contact with other flanges of the post  100 . As best seen in  FIG. 3 , the distance by which the resting ledge  28  projects from the shaft  12  is greater than the projecting distance of the braces  22   a ,  22   b , whereby this horizontal shifting of the braces into engagement with the post acts to place the resting ledge  28  in a position overlying the top end of the post, thereby effectively seating or hanging the post puller on the post  100 . The side walls  44  beneath the resting ledge prevent the post puller from falling laterally off the top end of the post. 
     Turning back to  FIG. 5 , a strap, cable, chain, rope or other flexible lifting line  104  is connected to the lifting member  16 , for example by coupling a clevis  106  to the lifting member  16  by way of a clevis pin  108  fed through the coupling point hole  30  at the top of the lifting member  16 . The other end of the flexible lifting line  104  is securely fastened to the lifting arrangement of a skid steer loader, front end loader, excavator, back hoe or other working machine having a raisable and lowerable lifting arrangement. The lifting line  104  may be coupled to a bucket or other implement mounted on the lifting arms or boom of such a working machine, or coupled directly to the lifting arms or boom if a suitable connection point is found thereon. The flexible lifting line may be connected to the lifting member of the post puller prior to placement of the post puller onto the post, and optionally used to help in the initial lifting of same, provided that the final placement of the post puller onto the post is performed manually so as to leave slack in the lifting line so that the upward pulling force on the lifting member is removed to allow the grippers to move into their default open position in which the gap space between them is greater than the width of the flange or web of the post. 
     With post puller seated atop the post, as shown in  FIG. 5 , the lifting arrangement of the working machine is raised, thereby pulling upward on the lifting member  16  of the post puller to cause the gripping surfaces of the grippers  20  to move toward one another and frictionally grip the web or flange  102  of the post  100  between them, whereupon continued raising of the lifting arrangement of the working machine will pull the post free from the ground. 
     As best shown in  FIG. 3 , each link  18  of the illustrated embodiment is made up of two matching link plates  18   a ,  18   b  disposed in front of and behind the plane of the lifting member  16  and grippers  20 , but it will be appreciated that each link may alternatively be defined by a single unitary piece. Likewise, although the inclusion of two braces  22   a ,  22   b  spaced notably apart along the longitudinal direction of the shaft provides an effective stabilizing function to keep the post puller  10  in-line with the post  100 , it may be possible to rely on only a single brace, or to even omit the braces altogether without detriment to the gripping and pull efficiency of the post puller  10 . Likewise, the inclusion or configuration of the handles may vary, although the use of two obliquely oriented handles  26  that extend both rearwardly and laterally from the shaft provide for a confident two-handed grip that is balanced across the shaft while keeping the user&#39;s hands well back from the post/puller interface during use to avoid inadvertent injury. 
     Although the use of rectangular tubing maintains proper alignment of the lifting member and links with the shaft-carried grippers at the front side of the shaft, tubing of other non-circular cross-sectional shape may similarly maintain such alignment by preventing relative rotation between the shaft and sleeve to minimize stress on the linkage. Alternatively, circular tubing may be used, either with suitable anti-rotation means acting between the shaft and tube or relying on the linkage itself to self-maintain alignment between its components. Although a hollow shaft is in the best interest of weight reduction and material efficiency, the invention is not limited specifically to the use of a hollow tubing to define the guide shaft for the sliding movement of the sleeve. 
     In addition to being usable on the post types mentioned in the background section above in the context of temporary fencing, the present invention can also be used with others post types that similarly have an accessible web or flange engagable by the grippers, for example including angle iron or U-channel posts used for road signage support or other ground-embedded applications. 
     Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the scope of the claims without departure from such scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.