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.
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.
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.
One embodiment of the invention will now be described in conjunction with the accompanying drawings in which:
In the drawings like characters of reference indicate corresponding parts in the different figures.
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'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 36a 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 20a 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 22a 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 22b 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 22a, 22b 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 22a on opposite sides of the shaft 12. In the illustrated embodiment, the resting ledge 28, upper brace 22a 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 22a 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 26a 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 26b likewise juts horizontally outward from the shaft at an oblique angle matching that of the lower arm 26a, but farther up the shaft 12, for example at the same elevation as the upper brace 22a. A central span 26c of each bar-type handle spans vertically between the upper and lower arms 26a, 26b 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 20a of the grippers 20, this causes the gripping surfaces 20a to move closer together across the central longitudinal plane of the shaft 12, thereby reducing the width of the gap or space therebetween.
With reference to
Turning to
Turning back to
With post puller seated atop the post, as shown in
As best shown in
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.
Number | Name | Date | Kind |
---|---|---|---|
1774661 | Otto | Sep 1930 | A |
4422621 | Ekern | Dec 1983 | A |
4721335 | Krenek, Jr. | Jan 1988 | A |
5011117 | Youngblood et al. | Apr 1991 | A |
5368277 | Moss | Nov 1994 | A |
5868060 | Plank | Feb 1999 | A |
7059587 | Fimple | Jun 2006 | B1 |
7290754 | Mensi et al. | Nov 2007 | B2 |
7963051 | Ford | Jun 2011 | B2 |
8453993 | Davis | Jun 2013 | B2 |
8608132 | Allen | Dec 2013 | B1 |
20020063245 | Salman | May 2002 | A1 |
20070183121 | Futrell | Aug 2007 | A1 |
20090028649 | Ringelstetter et al. | Jan 2009 | A1 |
20120279737 | Trethewey | Nov 2012 | A1 |
20130069025 | Schooley | Mar 2013 | A1 |
20130099184 | McNeill | Apr 2013 | A1 |
20160230414 | Lawrence | Aug 2016 | A1 |
Number | Date | Country |
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2012116405 | Sep 2012 | WO |
Number | Date | Country | |
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20160230414 A1 | Aug 2016 | US |