Post driving attachment for tractor

An apparatus for driving posts into the ground, comprises a hammer for striking the top of the post to be driven, an articulated arm for connecting the hammer to a mobile power unit; and means for raising the articulated arm so that the hammer is above the post. The hammer is pivotally connected to the arm so that the hammer will strike the top of the post generally squarely when the power unit is level and when the power unit is not level.

BACKGROUND OF THE INVENTION 
This invention relates to an apparatus for driving posts into the ground. 
Post drivers commonly include a heavy hammer which is raised above the post 
to be driven and the inertia gained by the heavy hammer falling towards 
the post causes the post to be driven into the ground as the hammer 
strikes the post. Post drivers preferably include a guide for holding the 
post in position until it is driven into the ground. Some post drivers, 
for example as disclosed in U.S. Pat. No. 3,302,731 to Perry, employ a 
guide frame with a hammer slidable on the frame to a position above the 
top of the post. 
Some prior art post drivers have been, however, relatively complicated and 
heavy. Not only does their heavy weight increase shipping costs of the 
equipment, but makes their use difficult on soft ground when attached to 
mobile equipment. When post drivers are provided as attachments, for 
example on tractors, a second man may be required for operation of the 
post driver besides the tractor operator. 
SUMMARY OF THE INVENTION 
According to this invention, there is provided an apparatus for driving 
posts into the ground. The apparatus comprises a hammer for striking the 
top of a post to be driven, an articulated arm for connecting the hammer 
to a mobile power unit, the hammer being pivotally connected to the arm so 
that the hammer will strike the top of the post generally squarely when 
the power unit is level and when the power unit is not level, and means 
for raising the articulated arm so that the hammer is above the post. 
The invention provides an apparatus for driving posts which is simple and 
economical to produce and is also relatively light weight. The reduction 
in weight over some prior art post drivers reduces shipping costs and 
allows tractors to move more easily over soft ground when such an 
apparatus for driving posts is provided as an attachment. The present 
apparatus is considerably easier to set up at the site where a post is to 
be driven and is more easily moved from site to site, since there is no 
ground supported frame, and the proper orientation of the hammer is 
assured regardless of whether or not the tractor is level. It is quite 
feasible for one man to operate the tractor and the apparatus for driving 
posts according to the invention. The configuration of the present 
invention allows its operation over obstructions, such as rock piles, 
which may be positioned between the tractor and the site where the post is 
to be driven.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1 and 2 show an apparatus 10 for driving posts into the ground. The 
apparatus 10 is mounted on a tractor 12 and includes a frame 14. Frame 14 
has a pair of upright members 16 and 18 attached to lugs 20 and 22 at the 
rear of the tractor near the ground. The top of the uprights 16 and 18 are 
attached at their upper ends to braces 24 and 26 respectively. Braces 24 
and 26 are attached to lugs 27 and 29 of uprights 28 and 30 which are 
welded to the frame of the tractor 12. 
The apparatus 10 has an articulated arm 31 comprising adjacent parts 32 and 
33 and having a proximal end 34 pivotally attached to the frame 14 
adjacent lugs 20 and 22 of the tractor 12 by link pins 35 and 36. The 
apparatus 10 also has a connecting link 37 having a proximal end 38 
pivotally connected for vertical movement to frame 14 near the tops of 
upright members 16 and 18 by means of connecting link swivel 39, cross bar 
40, and link pins 41 and 42. Connecting link swivel 39 permits rotation of 
connecting link 37 about an axis 44 passing through the proximal end 38 
and the distal end 46 of connecting link 36. Articulated arm 31 has a 
distal end 48 pivotally connected to connecting link 37 by means of 
bearing block 50 and link pin 52. Bearing block 50 has a bearing 54 
permitting rotation of connecting link 36 about axis 44 and permitting 
movement of bearing block 50, and distal end 48 of articulated arm 31, 
along connecting link 37 parallel to axis 44. 
The apparatus 10 also includes a hydraulic cylinder 56 pivotally connected 
to lug 58 of tractor 12 by link pin 60. Rod 62 of cylinder 56 is pivotally 
connected by link pin 68 to crossbar 64 connected between links 66 and 67. 
Links 66 and 67 are pivotally connected to lugs 69 and 70 of tractor 12 
near by link pins 71 and 72. Links 66 and 67 are pivotally connected to 
links 73 and 74 respectively by means of link pins 75 and 76. Link 73 and 
74 are pivotally connected to lugs 77 and 78 of articulated arm 31 by link 
pins 79 and 80 (not shown). 
The apparatus 10 is also provided with a hammer 90 pivotally connected to 
distal end 46 of connecting link 37 by means of fork 92 and link pin 94. 
Hammer 90 has a box-shaped depending guide 96 having an open end 98 on the 
bottom thereof. Guide 96 has an access door 100 having hinges 102 and 104, 
for permitting post 111 to be placed within guide 96, and latch 105. Latch 
105 comprises bar 107 welded to guide 96 and passable through elongated 
aperture 106 in bar 108 welded to door 100. A peg (not shown) is placed in 
aperture 109 of bar 107 to keep the door 100 shut. Adjusting plate 110 
permits adjustment of guide 96 for posts 111 of different sizes. Threaded 
studs 112 and 114 have one end attached to plate 110 and pass through 
apertures 116 and 118 respectively in side 113 of guide 96. Nuts 120 and 
122 on studs 112 and 114, respectively, permit adjustment of plate 110 
towards side 113. Bolts 124 and 126 are threaded through side 113 to 
permit adjustment of plate 110 away from side 113. 
In operation, articulated arm 31 is first raised by means of cylinder 56 
acting through links 66, 67, 73 and 74. As arm 31 moves upwards, bearing 
54 permits bearing block 50 to slide along connecting link 37 towards 
connecting link swivel 39 and lifts distal end 46 of connecting link 37 
away from the ground. When hammer 90 and depending guide 96 have been 
raised sufficiently high just before open end 98 clears the top of the 
post to be driven, as shown in dotted lines, access door 100 may be opened 
on hinges 102 and 104 and a post 111 placed within depending guide 96. It 
is important to note that the centre of gravity of hammer 90 and and 
depending guide 96 is located below link pin 94 connecting hammer 90 to 
fork 92 and connecting link 37 and below axis 44. Consequently, 
gravitational forces align the depending guide 96 to hold a post 111 
generally vertical, regardless of the position of arm 31, connecting link 
37, or whether or not the tractor 12 is level, by rotating hammer 90 and 
depending guide 96 about link pin 94 and axis 44. This is a particularly 
desirable feature where the tractor 12 and apparatus 10 must be operated 
on rough or uneven surfaces. There is no need to align the anvil 90 and 
guide 96 in any manner, since the guide 96 will align itself properly in a 
pendulum-like manner, and hammer 90 will strike the post 111 squarely, 
even if the tractor 12 should not be level. The post 111 is driven into 
the ground by allowing hydraulic fluid to freely escape from cylinder 56, 
whereby articulated arm 31 and connecting link 37 swing towards the ground 
and hammer 90 strikes post 111. Besides hammer 90, the momentum gained by 
articulated arm 31 and connecting link 37, in their downwardly swing, act 
upon post 111 as hammer 90 strikes post 111, thus increasing the driving 
force. The automatic alignment feature of the hammer 90 and depending 
guide 96 of the present invention makes quite feasible the operation of 
the tractor 12 and the apparatus 10 by one man. It should also be noted 
that the configuration of the apparatus 10 readily allows posts to be 
driven beyond obstructions between the tractor 12 and the position where 
the post is to be driven. As best seen in FIG. 2, the deviation of hammer 
90 and guide 96 from vertical alignment with post 111 is slight as the 
hammer 90 and guide 96 move in the arcuate path between the raised and 
lowered positions. This is important for the proper operation of such an 
apparatus.