Post puller

A machine for extracting an elongate work piece from a medium in which it is imbedded. The machine includes a vertical gripping plate in opposed gripping relating with an eccentrically pivoted gripper. These gripping elements are carried on a rigid frame adapted for attachment to the three point hitch lifting mechanism found on tractors. When the work piece is gripped between the gripping elements, lifting of the frame by means of the lifting mechanism of the tractor, will extract the work piece. Auxiliary lifting force may be provided with optional fluid power operated cylinders. Linkages may optionally be provided to remotely move the pivoted gripper into and out of gripping relation. The linkages may be operated manually or with a hydraulic or other power operated cylinder.

BACKGROUND OF THE INVENTION 
This invention relates to a machine and method for extracting fence posts, 
drills or other elongate work piece from the ground or other medium in 
which they may be imbedded. Particularly, it relates to such a device 
which is adapted for attachment to and operation from the three point 
hitch of a farm tractor or similar machine. 
Various devices have been previously disclosed which can be attached to a 
tractor or other machine and used to pull a fence post or drill or the 
like. Some of these are large and awkward and unsuitable for a relatively 
small tractor, others require that the operator of the tractor dismount 
and manipulate parts of the puller to engage it with the work piece or 
require a second person to perform this operation, some provide only 
limited engagement with the work piece and do not secure a sufficient grip 
to remove a work piece that is firmly imbedded and others use power 
operated grippers or other power appliances which make them large, 
cumbersome and expensive. Another objectionable feature of some of the 
prior art devices is that their gripping or pulling structure tends to 
impart rotational motion to the work piece being pulled. This makes it 
more difficult to pull the work piece and may bend or break it. In some 
cases when the work piece is pulled clear of the medium in which it is 
imbedded the rotational force applied may cause it to twist violently, 
potentially causing damage to the machine or injury to persons in the 
vicinity. The invention disclosed herein is designed to avoid all of these 
objectionable characteristics. 
SUMMARY OF THE INVENTION 
For clarity and simplicity the invention is described and illustrated with 
respect to its use for pulling fence posts. The invention consists of a 
base frame provided with means for attaching it to the three point hitch 
mechanism of a tractor and including a vertical gripping plate which has 
teeth for engaging a fence post to be lifted out of the ground. An 
eccentrically pivoted gripper is provided in opposed relation to the 
gripping plate and is also provided with gripping teeth. When the device 
is positioned with the gripping plate adjacent one side of a post to be 
removed and the pivoted gripper contacting the other side of the post, 
lifting of the frame by means of the lifting mechanism provided on the 
tractor will cause the post to be more tightly gripped because of the 
eccentric pivoting of the gripper and as lifting continues the post will 
start to move out of the ground. The attaching links of the three point 
hitch are attached to the base frame in such a manner that they will 
remain parallel to each other during the lifting operation imparting a 
substantially linear motion to the post as it is being pulled out of the 
ground. As will be explained in greater detail the pivoted gripper may be 
rotated on its pivot by friction and gravity to open and close as required 
to engage and release a post but preferably a spring may be provided to 
help urge it into engaging position and manual or power operated linkages 
may also be provided to control the engagement and disengagement of the 
pivoted gripper with a post being pulled. A substantial range of 
adjustment is available due to the eccentric mounting of the gripper but 
the device can be made to work on an even greater range of post sizes by 
providing adjustment of the position of the vertical gripping plate. 
It is an object of this invention to provide a post puller which is simple 
in construction but durable and effective in use. 
It is another object of this invention to provide a post puller for 
attachment to the three point hitch of a tractor and which can be used by 
the operator of the tractor without the necessity of dismounting to engage 
or disengage the puller from the post. 
Another object of this invention is to provide such a post puller which is 
attached to the three point hitch of a tractor in such a manner as to 
apply a generally vertical force to the post being pulled rather than an 
arcuate force tending to rotate the post along its length. 
Still another object of this invention is to provide a puller capable of 
pulling not only wooden posts but also metal pipes, steel rods, drills and 
other large smooth objects from the ground or from a medium in which they 
may be imbedded. 
Another object of this invention is to provide a post puller which will 
work with posts of a wide range of lengths and diameters and virtually any 
cross sectional shape. 
These and other objects, features and advantages of this invention will 
become apparent from the following description in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 1 and 2, it will be seen that the apparatus of the 
invention comprises a base frame 1 which may be constructed of square or 
box tubing as shown or of any other suitable structural elements. The base 
frame is constructed of vertical frame members 2 and 3 and horizontal 
frame members 4 and 5. The frame members are welded together or otherwise 
permanently joined to form a rigid substantially rectangular base frame 
which has a substantially unobstructed smooth, flat face 67. A pair of 
center mounting plates 6 and 7 extend between horizontal frame members 4 
and 5 and are welded or rigidly secured thereto to provide a connection 
point for the end 9 of center link 8, a freely pivoting link which is a 
part of the three point hitch of a tractor. Mounting plates 6 and 7 may be 
made of angle iron as indicated and have a corresponding series of holes 
10 as best seen in FIG. 4, for receiving a bolt or pin (not shown) by 
which the center link 8 is connected to the base frame. Support shafts 11 
and 12 are rigidly secured to the base frame as by welding to provide a 
place for connection of the pivot links 13 and 14 to the base frame. 
Lifting links 15 and 16 are pivoted in unison in a vertical plane under 
power from the tractor and are pivotally connected to the pivot links 13 
and 14. Lifting links 15 and 16 will raise or lower pivot links 13 and 14, 
which in turn will cause the base frame 1 to be raised or lowered 
vertically when the three point hitch mechanism is activated. Center link 
8 and links 13, 14, 15, and 16 are all parts of the three point hitch 
mechanism of the tractor and form no part of this invention. They are 
shown herein for purposes of illustration only. When connecting the 
implement to a tractor, the connection between center link 8 and the 
center mounting plates 6 and 7 is made at the mounting hole 10 which will 
place center link 8 in a position parallel with the position of pivot 
links 13 and 14 and its length adjusted so that it is approximately the 
same length as the latter. Center mounting plates are constructed so the 
holes 10 lie in approximately the same vertical plane which includes the 
axes of the support shafts 11 and 12. This will cause a post being pulled 
out of the ground to remain in a substantially vertical position as it is 
raised so that it will be pulled with the least amount of resistance and 
avoid any tendency of the post to rotate when it is pulled out of the 
ground. 
A vertical gripping plate 18 is provided with a series of gripping teeth 17 
which are welded or otherwise rigidly secured thereto. The gripping plate 
is secured to a support angle 19 which in turn is secured, as by bolts 20, 
to vertical frame member 2. Gripping plate 18 may be secured to the 
support angle 19 by means of a series of bolts 22. Alternate threaded 
holes 23 and 24 may be provided in horizontal frame members 4 and 5 to 
provide for step-by-step adjustment of the position of the gripping plate 
18 to handle different ranges of thicknesses or diameters of fence posts 
or other work pieces. Variations in size of the work piece within a given 
range are handled by the eccentric pivoting of pivoted gripper 25 as will 
hereinafter be more completely described. Support angle 19 is reinforced 
by means of triangular gusset plates 28 rigidly secured thereto as by 
welding. Pivoted gripper 25 comprises a back plate 26, contact plate 27 
permanently attached to said backing plate, as by welding, and reinforced 
with gusset plates 29 which may be of triangular shape. Gripper 25 is 
positioned so that contact plate 27 is in opposed relation with gripping 
plate 18 and is pivoted by suitable means to horizontal frame member 4. 
The distal end 63 of contact plate 27 is curved and the center of the 
pivot means between gripper 25 and horizontal frame member 4 is located 
eccentrically with respect to the curvature of contact plate 27. 
Therefore, as gripper 25 pivots downwardly as shown in FIGS. 1 and 2 the 
distance between gripping plate 18 and the opposing surface of contact 
plate 27 will decrease. As shown in FIG. 3, the pivot means between 
gripper 25 and horizontal frame member 4 may consist of a shaft 30 having 
an enlarged hub or disc 31, a bushing 32 mounted in the frame member, a 
retaining bolt 33 and washer 34, and a series of attaching bolts 35 for 
engaging threaded bones (not shown) in said hub whereby the gripper 25 may 
be mounted on the hub 31. A centering projection 51 may be formed 
integrally with hub 31 and pivot shaft 30. In such case, back plate 26 is 
provided with a bore 52 closely approximating the diameter of projection 
51. As will be obvious to those skilled in the art, various other means of 
mounting gripper 25 to the frame 1 may be provided including, for example, 
a fixed axle (not shown) projecting from horizontal frame member 4 and a 
hub (not shown) suitable retained on said axle and provided with roller or 
other form of bearings (not shown) for rotation on said axle. Pivoted 
gripper 25 is biased toward its horizontal position by a spring 36 which 
has one end hooked into an aperture 37 in the back plate of the gripper 
and has its other end engaged in an aperture 38 in a spring retainer 
suitably attached to vertical frame member 3 as, for example, by a bolt 
40. 
As will be explained later, the implement can be made to operate 
efficiently without any additional mechanism connected with the pivoted 
gripper. However, it has been found desirable to provide positive 
operating means as will now be described: A tab or extension plate 41 is 
provided on the back plate 26 of pivoted gripper 25 which is connected by 
a connecting rod 42 to a pivoted link 43. A handle 44 is made integral 
with link 43 and extends substantially at right angles thereto in a 
position where it may be grasped and manipulated by the operator of the 
tractor. A suitable extension or handgrip 66 may be provided to facilitate 
operation of the link 43 by the operator of the tractor. The link 43 and 
handle 44 are pivotally supported by a pivot pin 46 connected to an 
extension plate 45 which is rigidly secured to vertical frame member 3 by 
welding or other suitable means. Connecting rod 42 is pivotally connected 
at one end to the distal end of pivoted link 43 and is pivoted at its 
other end by pivot 47 to the tab 41 on gripper 25. 
FIG. 6 shows an alternate form of operator for controlling the position of 
pivoted gripper 25 in which a double-acting hydraulic cylinder 49 is 
connected between tab 41 on the gripper 25 and extension plate 45 in a 
manner well known in the art. Extension or retraction of piston rod 50 
will impart the desired pivotal movement of pivoted gripper 25. In this 
embodiment of the invention, biasing spring 36 shown in FIG. 2 may be 
dispensed with. 
Optional auxiliary gripping teeth as shown at 59 and 60 in FIG. 2 may be 
provided on the horizontal frame members 4 and 5 respectively. 
FIG. 5 shows the details of the gripping teeth and their mounting on 
vertical gripping plate 18. Each gripping tooth is cut so that the angle 
between its front face 55 and its top surface 54 is approximately 45 
degrees. The teeth are mounted so that the angle between the bottom edge 
57 of the tooth where it joins the gripping plate is approximately 15 
degrees above a horizontal line indicated by the numeral 56 and so that 
the angle between the top surfce of the tooth and the vertical face of 
plate 18 is approximately 75 degrees. These angles are in no way critical 
but appear to improve operation of the post puller as will be described 
later. 
If it is desired to provide auxiliary lifting power to extract trees or 
other firmly imbedded work pieces, the horizontal frame member 5 may be 
provided with brackets 68 rigidly secured to frame member 5, as by 
welding, and reinforced by gusset plates 69. Hydraulic cylinders 70 are 
secured to brackets 68 and have their piston rods 72 suitably attached to 
pads 71. As force is being applied through the three point hitch lifting 
mechanism, pressure fluid may also be directed to the cylinders 70 to 
extend the piston rods 72 until pads 71 contact the ground 73. Further 
extension of piston rods 72 will apply a lifting force to horizontal frame 
member 5, base frame 1 and the work piece. 
OPERATION OF THE INVENTION 
To connect the machine to a three point hitch, the pivot links 13 and 14 
are slid over the axles 11 and 12 and retained there as by washer 61 and 
cotter pin 62. The center link 8 is adjusted and positioned so that it can 
be engaged with one of the sets of mounting holes 10 in the mounting 
plates 6 and 7 in a position in which the link 8 will be substantially 
parallel with and substantially of the same length as the links 13 and 14. 
Link 8 is then pivotally connected to mounting plates 6 and 7 by suitable 
means such as a bolt and nut (not shown). The base frame is then raised by 
means of the three point hitch and the implement is backed up to a post to 
be removed. Gripping plate 18 will have previously been adjusted to a 
position in which the minimum gap between gripping plate 18 and the toe or 
distal end 63 of contact plate 27 is substantially less than the thickness 
of the post to be removed when the gripper 25 is in its horizontal 
position substantially as illustrated in FIG. 1. The distance between 
vertical gripping plate 18 and the opposite end 64 of contact plate 27 
when the pivoted gripper 25 is in its substantially vertical position 
should also be greater than the maximum thickness of the range of 
thicknesses of the posts to be worked on. The implement is backed into the 
post so that the arcuate portion 30 of the contact plate 27 is in slight 
frictional engagement with the post. The base frame is lowered by means of 
the three point hitch while the tractor is held stationary or continues to 
be moved slightly toward the post. The gripper 25 will be pivoted toward 
its open position and, since there will be a slight arcuate movement of 
the base frame toward the post and be positioned on either side of it. The 
post will be positioned between the gripper plate 18 and the contact plate 
27 and be engaged by the teeth 17 and 65 respectively. The three point 
hitch is then moved to its lower-most position and then raised. As the 
three point hitch is lowered, the gripping teeth will slide freely down 
along the post, tending to slightly open the gripper. Raising the three 
point hitch, and consequently, the base frame, will cause the teeth 17 and 
65 to bite into the post gripping it tightly and eventually will begin to 
move it upward out of the ground. If the post in imbedded in the ground a 
greater distance than it can be pulled up by one stroke of the three point 
hitch mechanism, the base frame is lowered and raised, with the results 
described above, as many times as is necessary to completely extract the 
post from the ground. When the post is extracted, the three point hitch 
mechanism is raised to a position at or near the top of its stroke and 
then lowered. The bottom end of the post is allowed to strike the ground 
and the three point hitch mechanism continued to be lowered. This will 
cause the post to be released and to fall out of the grip of the gripper. 
According to the foregoing description of operation the implement may be 
operated without external means to pivot the gripper 25. However, it is 
preferred to provide means previously described, including handle 44 and 
connecting rod 42, to permit manual operation of gripper 25. The gripper 
may be held in its open position with the mechanism just referred to as 
the tractor is backed up to the post. The gripper is then pivoted closed, 
the three point hitch mechanism lowered then raised to extract the post as 
previously described. The operation is the same when a hydraulic cylinder 
49 is provided except that the opening and closing of the pivoted gripper 
is effected by the power means rather than manually. 
It can be seen that as force is applied to raise the post the inclination 
of the teeth on the gripping plate 18 will tend to cause the post to slide 
inward toward the horizontal frame members 4 and 5 and will overcome any 
tendency of the implement to lose its grip on the post. If optional 
auxiliary teeth 59 and 60 are provided a still stronger grip of the post 
will be provided when it slides back far enough to engage the auxiliary 
teeth. The inclination of the teeth above the horizontal will hold the 
post against sidewise slippage, while the sharp edge formed by the angle 
between the surfaces 54 and 55 of the teeth will increase their tendency 
to bite into and lift the post. 
As the three point mechanism is lifted from a position where the links 8, 
13 and 14 slope downward toward the ground from front to rear of the 
tractor, the base frame 1 will remain in a substantially vertical position 
as it is lifted but the entire frame will move in a slightly arcuate 
motion rearward toward the post until the links reach a position 
substantially parallel with the ground. This will further cause the post 
to move into the base frame and into engagement with the horizontal frame 
members 4 and 5 or the auxiliary gripping teeth 59 and 60. As the links 8, 
13 and 14 continue to move upward past the horizontal position the base 
frame will be moved in a slightly arcuate path in a direction away from 
the post. However, the tight grip of the post by the gripping mechanism 
coupled with the angle at which the teeth are mounted on the gripping 
plate prevent the escape of the post from the gripping mechanism. It is 
further found that if the tractor is not locked in position with respect 
to the ground, a slight forward and back motion of the tractor will result 
but the base frame will remain in and be moved in a substantially vertical 
plane. Any tendency of the mechanism and post to be rotated about the axis 
of the shafts 11 and 12 will be substantially completely obviated. 
If the device is provided with the auxiliary lifting mechanism previously 
described and it is desired to utilize the auxiliary lift capability, 
pressure fluid is admitted to the cylinder 70 to extend piston rod 72 at 
the time when the three point hitch mechanism is activated to apply lift 
to base frame 1 and pressure fluid is routed to retract piston rod 72 when 
the three point hitch mechanism is lowered. 
Operation of the invention has been described above in connection with its 
use to pull out posts or other work pieces of wood or other substantially 
soft material into which the gripping teeth will bite for improved grip. 
When it is desired to pull pipe, metal fence posts, drills or similar 
items, the vertical gripping plate 18 shown, which is provided with teeth 
17 may be removed by removing the bolts 22 and replaced with an alternate 
gripping plate (not shown) provided with a rubber or other elastomeric or 
plastic gripping surface or with other frictional material. This 
alternative gripping plate could be used with the pivoted gripper as shown 
or with one which is also provided with one of the frictional gripping 
surfaces described above. 
It is to be understood that the invention disclosed herein is not limited 
to the details of construction and arrangement of parts illustrated in the 
accompanying drawings but is capable of being practiced or carried out in 
various ways. Furthermore, the terminology employed herein is for the 
purpose of description only and is not to be considered as a limitation. 
It is obvious to those skilled in the art that although the invention has 
been shown and described in one or more preferred embodiments, many 
variations may be made in the form and structure here presented without 
departing from the scope of the present invention as set forth in the 
appended claims.