Fork lift attachment for tractor

A fork lift attachment for a tractor. The fork lift attachment includes a subframe having a pair of arms that are attached to the sides of the tractor. A mast is pivoted to the outer end of the subframe and is adapted to be pivoted in a fore and aft direction by a hydraulic cylinder unit. Mounted for movement on the mast is a fork rack and a sliding rack, which carries the lift forks, is mounted for lateral movement on the fork rack. A pair of lift cylinders are mounted along the sides of the mast and operate to move the fork rack and lift forks relative to the mast, while a shift cylinder interconnects the fork rack and the sliding rack to shift the sliding rack and forks in a lateral direction. The lift cylinders are spaced apart to provide an opening for the power take-off of the tractor so that the fork lift attachment does not interfere with normal operation of the power take-off or the three-point hitch system.

BACKGROUND OF THE INVENTION 
The conventional three-point hitch system is used with a tractor to operate 
implements such as a tiller, scoop, gang mower, rotary mower, post hole 
digger, pulverizer, plow blade, or the like. Frequently, there is also 
need for a fork lift for loading operations, and fork lifts have been 
designed for mounting on the three-point hitch system of the tractor, as 
shown in U.S. Pat. Nos. 2,868,399 and 4,394,107. 
However, a fork lift attachment as mounted on the three-point hitch system 
has certain limitations. Initially, this type of fork lift attachment is 
only capable of lifting a maximum of 3,000 lbs. and generally only about 
1,500 lbs. Further, it is necessary to remove the fork lift attachment 
from the three-point hitch system in order to use other implements with 
the tractor. 
SUMMARY OF THE INVENTION 
The invention is directed to an improved fork lift attachment for a tractor 
in which the fork lift attachment is independent of the three-point hitch 
system, thus leaving the three-point hitch system free for mounting of 
other implements. 
In accordance with the invention, the fork lift attachment includes a 
sub-frame having a pair of generally parallel spaced arms which are 
attached to the sides of the tractor. A mast is pivoted for fore and aft 
movement on the outer end of the sub-frame and a cylinder unit 
interconnects the sub-frame and the mast to provide the pivotal fore and 
aft movement through an arc of about 10.degree.. 
Mounted for movement on the mast is a fork rack, and a sliding rack, which 
carries the lift forks, is mounted for lateral movement on the fork rack. 
The fork rack and lift forks are raised and lowered by a pair of lift 
cylinders which are mounted along the sides of the mast, and the central 
portion of the mast is open to receive the power take-off and central link 
of the three-point hitch. 
The sliding rack which carries the lift forks can be moved laterally 
relative to the fork rack by a shift cylinder which interconnects the two 
racks. 
Other objects and advantages will appear in the course of the following 
description.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
The drawings illustrate a fork lift attachment 1 for a tractor 2. The fork 
lift attachment can be permanently connected to the tractor and will not 
interfere with the use of other three-point hitch implements such as 
pulverizers, plow blades, rotary mowers, scoops, post hole diggers, and 
the like. 
The fork lift attachment 1 includes a sub-frame 3 composed of a pair of 
generally parallel side members 4 which which are connected together by 
cross members 5. The free ends of side members 4 are provided with 
upwardly extending brackets 6 which are bolted to the engine block 7 of 
the tractor. 
As best illustrated in FIGS. 2 and 3, the opposite end of the subframe 
includes a cross channel 8 and a vertical plate 9 is mounted edgewise on 
the upper surface of cross plate 8 and is provided with an opening 10 
through which the power take-off of the tractor extends. 
Extending rearwardly and upwardly from the subframe 3 are two pair of legs 
11 which are connected by a cross arm 12, and a vertical mast 13 is 
pivotally connected to legs 11. 
In addition, a post or pedestal 14 is attached to the outer end of subframe 
3, as shown in FIG. 2, and the upper end of the post carries the valve 
block 15 which controls the hydraulic system for the fork lift attachment. 
As shown in FIG. 2, side brackets 16 are secured to the sides of the outer 
end of subframe 3 and serve to space the outer arms of the three point 
hitch away from the subframe. 
Mast 13 is composed of a pair of spaced channel-shaped side members 17 
which are connected along their length by a central cross channel 18 and a 
top member 19. Mast 13 is adapted to be tilted with respect to the 
subframe to an angle of about 10.degree. in a fore and aft direction. The 
fore and aft tilt is employed to maintain the load on the lift forks in a 
generally horizontal attitude in the event the tractor is at an incline or 
moves over uneven terrain. 
To tilt the mast 13, a hydraulic cylinder 20 is mounted beneath subframe 3 
and one end of cylinder 20 is connected to one of the cross members 5 of 
the subframe, as illustrated in FIG. 3. The piston rod extends outwardly 
from the cylinder and is connected to the lower end of mast 13 at a level 
beneath the pivotal connection of the mast to the legs 11. By extending 
and withdrawing the piston rod, mast 13 can be pivoted in a fore and aft 
direction with respect to subframe 3. 
A fork rack 22 is mounted for vertical movement on mast 13. As best 
illustrated in FIG. 3, fork rack 22 includes an upper channel 23 and a 
lower channel 24 which are connected by vertical column. A pair of plates 
26 extend from channels 23 and 24 in a direction toward tractor 2, and a 
pair of upper rollers 27 are journaled on the upper corners of plates 26, 
while a pair of lower rollers 28 are journaled on the lower corners of 
plates 26 adjacent channel 24. Rollers 27 and 28 are adapted to ride 
against the forward and rear edges of the mast side members 17 as the fork 
rack 22 is raised and lowered. 
To raise and lower fork rack 22, a pair of lift cylinders 29 are utilized. 
As shown in FIG. 4, lift cylinders 29 are located along the sides of the 
mast 13 with a substantial space therebetween through which the power 
take-off and the central arm of the three point hitch extend. With this 
construction the mast 13 and lift cylinders 29 will not interfere with the 
normal operation of the power takeoff or three-point hitch. 
The lower ends of cylinders 29 are pivotally connected through lugs 30 to 
the lower end of mast 13. Piston rods 31 extend from the upper ends of 
lift cylinders 29 and sprockets 32 are mounted for rotatation on the upper 
end of each rod. A roller link chain 33 is engaged with each of the 
sprockets 32 and one end of each chain 33 is dead-ended on a bracket 34 on 
mast 13, while the opposite end of each chain is connected to a lift block 
35 on the fork rack 22. Extension and contraction of piston rods 31 will 
thereby raise and lower the fork rack 22 relative to the mast. The use of 
the chains 33 provides a greater length of travel for the fork rack 22 for 
each increment of movement of the piston rod. 
Mounted for lateral sliding movement on fork rack 22 is a sliding rack 36. 
To mount the rack 36 for sliding movement relative to rack 22, a rod 37 is 
mounted in spaced relation above upper channel 23 of fork rack 22 through 
lugs 38. The upper end of the sliding rack 36 is also provided with a pair 
of lugs 39 which are slidable on rod 37. To also aid in supporting the 
sliding rack 36 from fork rack 22, a lip plate 40 is attached to the upper 
surface of sliding rack 36 and extends rearwardly, i.e. in a direction 
toward tractor 2, over the upper surface of upper channel 23 of fork rack 
22. Lip 40 aids in supporting the sliding rack. 
As best illustrated in FIG. 5, sliding rack 36 comprises an upper channel 
41, a lower channel 42 and a pair of vertical connecting plates 43 which 
connect the side edges of upper and lower channels 41 and 42. A pair of 
forks 44 are secured to the channels 41 and 42 by U-clamps 45, 
respectively. 
To shift the sliding rack 36 laterally with respect to fork rack 22, a 
cylinder 46 is pivotally connected though clevis 47 to one of the vertical 
columns 25 of fork rack 22, while piston rod 48, which is slidable within 
cylinder 46, is connected through clevis 49 to one of the vertical bars 43 
of the sliding rack 36. By extending and withdrawing piston rod 48, the 
sliding rack 36 can move through a limited stroke of movement laterally 
with respect to the fork rack 22. This lateral movement enables the forks 
44, when carrying a load, to be shifted laterally relative to the fork 
lift attachment 1 and tractor 2 to move the load away from other loads, or 
to move a load tight up against an existing load. 
It is also contemplated that a mast mounted drawbar 50 can be utilized for 
towing certain types of implements. 
The fork lift attachment of the invention is mounted independently of the 
normal three-point tractor hitch system, thus leaving the three point 
hitch system free for mounting all three point hitch implements. 
The dual hydraulic cylinders 29 are mounted along the sides of the mast 13, 
which leaves the center space between the cylinders open to receive the 
center link of the three point hitch and the power takeoff. In addition, 
the spacing between the lift cylinders 29 provides better visibility for 
the operator during loading and transporting and during use of the power 
takeoff implements. 
The fork lift attachment of the invention is operated through the hydraulic 
system of the tractor, or alternately, by an auxiliary system. 
As the fork lift attachment of the invention is mounted independently of 
the three point tractor hitch system, the fork lift attachment does not 
have to be removed when using the three-point system. 
As a further advantage, the fork lift has a substantially increased lifting 
capacity over fork lift attachments connected to the three point hitch 
system of the tractor, thereby enabling greater loads to be lifted to a 
greater height. 
Various modes of carrying out the invention are contemplated as being 
within the scope of the following claims particularly pointing out and 
distinctly claiming the subject matter which is regarded as the invention.