Device for supporting lift roll for fork lift truck

This invention relates to a device for supporting a lift roll for a fork lift truck of the type in which the thrust in the fore and aft direction and in the transverse direction is supported solely by a lift roll, the contact pressure of the lateral side of the outer race with respect to the pressure-receiving section is adjusted by an adjustment screw.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a device for supporting a lift roll for a fork 
lift truck of the type in which the thrust in the fore and aft direction 
and in the transverse direction is supported solely by a lift roll. More 
particularly, it relates to a device for supporting the lift roll of the 
type in which the thrust in the transverse direction is supported by that 
the lateral side of the outer race abuts on a pressure receiving section 
formed on a web of a mast and in which the contact pressure of the lateral 
side of the outer race with respect to the pressure-receiving section is 
adjusted by an adjustment screw. 
2. Prior Art 
FIG. 1 shows a typical prior-art lift roll 4 of the type in which a 
transverse thrust is received by abutment of the lateral surface of an 
outer race 7 on a pressure-receiving portion 8c formed on a web 8b of an 
inner mast 8. The lift roll 4 is mounted to a roll pin 3 projectingly 
mounted as by welding to a rear plate 2 of a lift bracket 1 as shown. That 
is, an inner race 5 is fitted on the roll pin 3 for movement axially, 
while an outer race 7 is fitted on the inner race 5 for rotation, this 
outer race 7 being adapted for rolling longitudinally on a flange section 
8a as the lateral side of the outer race abuts on a pressure-receiving 
portion 8c formed on the web 8b of the inner mast 8. The contact pressure 
of the lateral side of the outer race on the pressure-receiving portion 8c 
is usually adjusted by a shim 25. The adjustment system of this type is 
shown for example in the Japanese Patent Publication No. 32819/1973. 
Another adjustment system using a screw is shown in FIG. 2 in which the 
inner race 5 is fitted with a bottom plate 5a one lateral side of which is 
closed by a plate. The bottom plate 5a is thrusted towards the inner mast 
8 by an adjustment screw 9 threadedly passed through central openings of 
the roll pin 3 and of the rear plate 2 of the lift bracket 1. This 
adjustment system is described for example in the Japanese Utility Model 
Publication No. 31674/1984. 
In the above described conventional lift rolls, the inner race 5 can be 
extracted from the roll pin 3 in both the adjustment system by the shim 25 
and the adjustment system by the adjustment screw 9. Thus, in case when 
flexure or distortion has occurred between the inner mast 8 and the lift 
bracket 1, there is the risk of the lift roll 4 dropping off the roll pin 
3 or the lift roll 4 being tilted to cause locking. This phenomenon of 
flexure or distortion between the inner mast 8 and the lift bracket 1 is 
likely to occur in case of application of a partialized load, that is, 
when the load is clamped in the acutely partialized state such as in the 
course of the material handling operation employing a rotary clamp, and 
the load is then relocated after inverting the load through 90.degree. or 
180.degree.. Since the left and right side inner masts 8 are arranged in 
the form of a letter eight narrowed at the ends in order to eliminate 
vibrations in the raised state, the lift roll 4 is liable to drop off the 
roll pin 3 when the lift bracket 1 is tilted relative to the inner masts 
8, as shown in FIG. 4. There is also, as shown in FIG. 3, the risk that 
the lift roll 4 be moved in the dropping direction relative to the roll 
pin 3 while being tilted and locked between the inner masts 8 and the roll 
pin 3 such that rotation thereof is inhibited. 
It is therefore an object of the present invention to provide a device for 
supporting a lift roll for a fork lift track that is free from the above 
described disadvantages of the prior art device. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided a device for 
supporting a lift roll for a fork lift, comprising an annular inner race 
slidably fitted on a roll in secured to a rear plate of a lift member, and 
an outer race rotatably fitted to said inner race, said outer race being 
adapted to roll along a flange section of an inner mast, with the lateral 
side of said outer race abutting on a web of said inner mast, wherein the 
improvement resides in that it further comprises a protruding portion 
formed towards said inner mast of said inner race and protruding a 
predetermined length from an end of said roll pin, an adjustment screw 
passed through and threaded engaged with said rear plate and roll pin, and 
retaining means for engaging said adjustment screw with said protruding 
portion and for causing said inner race and said adjustment screw to be 
moved in unison, the contact pressure of said outer race at said 
pressure-receiving section being adjusted by rotation of said adjustment 
screw. 
In the above arrangement, the contact pressure of the lateral sides of the 
outer race relative to the pressure-receiving section of the inner masts 
may be adjusted by screwing an adjustment screw to thrust the inner race 
outwards via the piston ring. After termination of such adjustment, since 
the inner race and the adjustment screw are engaged at all times with each 
other by the retaining means, the lift roll may be maintained at the 
adjustment position, so that the lift roll and the roll pin may be 
maintained at all times in the interengaged portion. 
According to the present invention, the contact pressure between the 
pressure-receiving section of the mast and the outer lateral side of the 
outer race may be adjusted by an adjustment screw, resulting in shortened 
adjustment time. Re-adjustment during application may be made without 
dismantling the lift bracket. Above all, dropping of the lift roll or the 
tilt of the lift roll relative to the roll pin or the mast incurring 
locking during the application of a partialized load in the course of the 
material handling operation may be avoided to maintain the smooth guide 
function by the lift roll.

EMBODIMENT 
Referring to FIGS. 5 to 10, certain illustrative embodiments of the present 
invention will be described in detail. In the first embodiment shown in 
FIGS. 5 and 6, 1 denotes a lift bracket as a lift member. Roll pins 3 are 
secured by welds 3c to the upper and lower outer lateral sides of a rear 
plate 2 provided via welds 2a to this lift bracket 1. Each roll pin 3 has 
a central screw hole 3a. A lift roll 4 is constituted by an annular inner 
race 5 fitting the roll pin 3 and an annular outer race 7 fitted for 
rotation on the outer periphery of the inner race 5. The inner race 5 thus 
fitted has a boss 5A protruding axially a predetermined length from the 
foremost part 3d of the roll pin 3. On the other hand, the outer race 7 is 
fitted in a recess 8A of an inner mast 8 having a channeled cross section 
and adapted to roll along a flange section 8a of the inner mast 8 to 
support the thrust in the fore and aft direction of a material handling 
device, not shown. The outer side of the outer race 7 abuts a 
pressure-receiving section 8c in the web 8b of the inner mast 8. It is 
noted that this pressure-receiving section 8c is formed by a thickened 
rear side portion of the web 8b. 
An adjustment screw 9 has a cross-shaped hole 9a at its one end and a 
hexagonal hole 9b at the other end, this cross-shaped hole 9a and the 
hexagonal hole 9b being used during assembling and adjustment, 
respectively. The one end 9A of the adjustment screw 9 is protruded out of 
the screw hole 3a of the roll pin 3. The projecting end is formed with a 
circular bulged portion 10 fitting with the inner peripheral portion of 
the boss 5A as later described. The other end 9B of the adjustment screw 9 
is passed through a through-hole 2b formed in the rear plate 2 of the lift 
bracket 1. The adjustment screw 9 is locked at the adjusted position by a 
nut 14 threaded to the protruding end and constituting a locking means. 
The end of the roll pin 3 is formed with a counterboared portion 3b for 
avoiding conflict with the bulged portion 10. An annular groove 11 for 
engaging with the screw and a groove 12 for engaging with the boss are 
formed on the outer peripheral surface of the bulged portion 10 in the 
adjustment screw 9 and on the inner peripheral surface of the inner race 5 
engaging therewith, respectively. That is, the adjustment screw 9 and the 
inner race 5 are unified to each other axially by the medium of a piston 
ring 13. The foremost part of the bulged portion 10 is tapered to 
facilitate the fitting of the piston ring 13. The bulged portion 10, 
grooves 11, 12 and the piston ring 13 constitute retaining means for 
allowing the inner race 5 and the adjustment screw 9 to be moved in 
unison. 
In the above described arrangement of the lift roll supporting device 
according to the present invention, adjustment of the contact pressure of 
the outer lateral side of the outer race 7 relative to the 
pressure-receiving section 8c of the inner mast 8 is performed in such a 
manner that, with the lift roll 4 attached to the roll pin 3 being fitted 
in the recess 8A of the inner mast 8, the adjustment screw 9 is screwed by 
a hexagonal rod wrench, not shown, to thrust the inner race 5 axially 
outwardly, that is, towards the inner mast 8, by the intermediary of the 
piston ring 13. After adjustment, the nut 14 is tightened for locking the 
adjustment screw 9 in the thus adjusted position. Such adjustment by the 
adjustment screw 9 may be made easily even when the contact pressure is 
changed due to wear of the contact portions through usage. 
When a partialized load acts during the material handling operation, as 
described hereinabove, such that flexure or distortion occurs between the 
inner mast 8 and the lift bracket 1 and, as a result, the inner mast 8 and 
the rear plate 2 are displaced in a direction away from each other, the 
lift roll 4 is prevented from dropping by virtue of the piston ring 13, 
while the trouble of the lift roll 4 being tilted and locking the roll pin 
3 or the inner mast 8 may be prevented from occurring. 
Although the above description has been made of the lift roll 4 for the 
lift bracket 1, the present invention may apply for the lift roll for the 
inner mast as well. The adjustment screw 9 may be engaged with the rear 
plate 2 instead of with the roll pin 3. 
Referring to FIGS. 8 and 9, a second embodiment of the lift roll supporting 
device for a lift truck according to the present invention. In these 
figures, the parts or components that are the same as those shown in FIGS. 
5 and 6 are depicted by the same numerals. In these figures, 1 denotes a 
lift bracket as a lift member. Roll pins 3 are secured by welds 3c to the 
upper and lower outer lateral sides of a rear plate 2 provided via welds 
2a to this lift bracket 1. Each roll pin 3 has a central screw hole 3a. A 
lift roll 4 axially slidably fitted on the outer periphery of the pin 3. 
The lift roll is constituted by an annular outer race 7 fitted for 
rotation on the outer periphery of the inner race 5. The inner race 5 has 
on its one lateral side a boss 5A having an inwardly bulged flange 5Aa 
having a central circular through-hole 5B. The outer race 7, on the other 
hand, is fitted in the recess 8A of the channel-shaped inner mast 8, and 
is adapted to roll along a flange section 8a of the inner mast 8 to 
support the thrust in the fore and aft direction of a material handling 
device, not shown. The outer side of the outer race 7 abuts a 
pressure-receiving section 8c formed in the web 8b of the inner mast 8. It 
is noted that this pressure-receiving section 8c is formed by a thickened 
rear side portion of the web 8b. 
An adjustment screw 9 has a cross-shaped hole 9a at its one end and a 
hexagonal hole 9b at its other end, this cross-shaped hole 9a and the 
hexagonal hole 9b being used during assembling and adjustment, 
respectively. The one end 9A of this adjustment screw 9 is protruded from 
the screw hole 3a of the roll 3 with the protruded end fitting in a 
central through-hole 5B in the flange section 5Aa of the inner race 5. An 
engaging flange 20 abutting on the inner surface of the flange section 5Aa 
of the inner race 5 is formed in the vicinity of the protruding portion 
from the screw opening 3a of the roll pin 3 of this adjustment screw 9, 
this engaging flange 20 receiving the lateral thrust acting on the inner 
race 5. The end of the roll pin 3 is formed with a counterbored portion 3b 
for avoiding possible conflict with the engaging flange 20. The protruding 
end of the adjustment screw 9 from the fitting shaft 9D formed in register 
with the flange section 5Aa is formed with an annular groove 9E. A snap 
ring 21 attached to this annular groove 9E abuts on the outer side of the 
flange section 5Aa of the inner race 5 to inhibit extraction of the lift 
roll 4 from the roll pin 3. On the other hand, the flange section 5Aa is 
sandwiched between the engaging flange 20 and the snap ring 21. The flange 
section 5Aa, engaging flange 20 and the snap ring 21 constitute retaining 
means whereby the inner race 5 and the adjustment screw 9 may be moved in 
unison. It is noted that the other end 9B of the adjustment screw 9 is 
passed through the through-hole 2b formed in the rear plate 2 of the lift 
bracket 1, and the adjustment screw 9 is locked in the adjusted position 
by a nut 14 threaded to the end portion and constituting the locking 
means. 
In the above described arrangement of a second embodiment of the lift roll 
supporting device according to the present invention, adjustment of the 
contact pressure of the outer lateral sides of the outer race 7 relative 
to the pressure-receiving section 8c of the inner mast 8 is performed in 
such a manner that, with the lift roll 4 attached to the roll pin 3 being 
fitted in the inner mast 8, the adjustment screw 9 is screwed by a 
hexagonal rod wrench, not shown, to thrust the flange section 5Aa of the 
inner race 5 axially outwardly via the engaging flange 20. After 
adjustment, the nut 14 is tightened for locking the adjustment screw 9 in 
the pre-adjusted position. Such adjustment by the adjustment screw 9 may 
be made easily even when the contact pressure is changed due to wear of 
the contact portions even if a contact pressure is changed through usage. 
When a partialized load acts during the material handling operation, as 
described hereinabove, such that flexure or distortion occurs between the 
inner mast 8 and the lift bracket 1 and the inner mast 8 and the rear 
plate 2 ar displaced in a direction away from each other, the lift roll 4 
is prevented from dropping by the snap ring 21 while the trouble of the 
lift roll 4 being tilted and locking the roll pin 3 or the inner mast 8 
may be prevented from occurring. 
A third embodiment of the present invention will be explained by referring 
to FIG. 10. In this embodiment, a piston ring 30 is employed as the 
retaining means for the lift roll 4. The flange section 5Aa in the 
protruding portion 5A of the inner race 5 is thickened, as shown, and 
engaging grooves 41, 42 are formed in register with the inner peripheral 
surface of the through-hole 5B of this flange section 5Aa and the outer 
peripheral surface of a fitting shaft 9D of the adjustment screw 9 fitting 
on the inner peripheral surface. A piston ring 30 is fitted in the annular 
grooves 41, 42. The present embodiment is otherwise the same as the above 
described embodiments so that the same numerals are used to depict the 
same or corresponding parts. Hence, in this third embodiment, it is 
possible to adjust the contact pressure of the outer race 7 with respect 
to the pressure-receiving section 8c of the inner mast 8 by the adjustment 
screw 9, in the same way as in the preceding embodiments, while inhibiting 
the accidental extraction of the lift roll 4. Thus the engaging flange 20, 
flange section 5Aa and the piston ring 30 constitute retaining means 
whereby the inner race 5 and the adjustment screw 9 may be moved in 
unison. 
Although the above description has been made of the lift roll 4 for the 
lift bracket 1, the present invention may apply for the lift roll for the 
inner mast as well. The adjustment screw 9 may be engaged with the rear 
plate 2 instead of with the roll pin 3.