Roll clamp

A roll clamp for handling of rolls or other loads carried by a lift truck. The clamp includes a rotator having a rear base plate for being mounted upon the lift mast of the truck, permitting it to be raised or lowered to a vertical position. A frame is gimballed to the rotator front plate. Extending forwardly from the clamp assembly is a pair of clamp arms which are swingably disposed, or pivot relative to the frame for closing and opening by movement toward and away from each other. The rotator rotates the frame relative to the mast about a clamp rotation axis. Hydraulic cylinders selectively open and close the arms, which have clamp pads at their distal ends for engaging the load surfaces. The rotator base plate carries a swash ring defining a plane skewed relative to the axis of clamp rotation. The frame includes rollers bearing against the ring to tilt the frame relative to the rotation axis as the clamp rotates, causing the clamp arms to skew relative to the pivot axis as the base is rotated and automatically causing one arm to overextend the other when the clamp arms are in an orientation for horizontal load disposition.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates to roll clamps for lift trucks or the like and, mcre 
particularly, to an improved roll clamp more readily permitting loads to 
be picked up when horizontal. 
Roll clamps as conventionally mounted upon the lift mast of lift trucks are 
intended to pick up, carry, transport and set down rolls of paper such as 
used for newsprint and other purposes, as well as drums, tube sections, 
gas cylinders and various other loads of cylindrical character. In the 
handling of such loads by means of a roll clamp of this type, the operator 
may be called upon to pick up the load which is standing on its end, i.e., 
with its axis of cylindricity vertical, as when paper rolls are 
transported by truck. After the rolls are transported, they must be set 
down in either horizontal or vertical orientation. If horizontal, rotation 
of the clamp is required. 
When a cylindrical load is disposed or picked up in horizontal orientation, 
such as when lying on the floor or ground, it is difficult to engage the 
load with the clamp pads unless the upper arm overreaches the lower arm. 
This problem is compounded also with regard to paper rolls which are full 
size when placed horizontally for being unrolled but are quite small when 
nearly used up. When a cylinder load is picked up in horizontal 
orienation, it often must be rotated to vertical position for stacking or 
transportion such as in a truck trailer, freight car, warehouse, etc. The 
limited space available in this situation requires delicate maneuvering of 
the lift truck. Although one arm of the clamp could be designed longer 
than the other so as to provide overreaching that arm when the load is 
horizontal, as in Bittner U.S. Pat. No. 4,209,280 and Farmer et al U.S. 
Pat. No. 4,160,260, this would present a difficulty when the rolls must be 
handled vertically in confined quarters as required during storage or 
transportation. In those situations, it is preferable to have the arms of 
equal length, and not be skewed to either side in front of the truck. 
To cause overreaching of one arm relative to the other, roll clamps have 
also been designed by offset pivoting of the arms offset from the axis of 
rotation of the roll clamp assembly and by utilizing auxiliary hydraulic 
cylinders to shift the arms offcenter about the pivot axis. Typical of 
such roll clamp configuration is that disclosed in Farmer et al U.S. Pat. 
No. 4,227,850. However, when the hydraulic cylinder is used to shift one 
of the arms forward relative to the other, the center of gravity of the 
load is necessarily displaced forwardly from the lift truck. Since rolls 
may weigh up to several thousand pounds, the forward relocation of gravity 
produces a substantial moment arm which imbalances the lift truck and 
consequently results in a derating of its load capacity. 
A further disadvantage of this overreach design is the need for as well as 
the cost and complexity of the hydraulic cylinder, which must be of 
considerable size appropriate to lifting such heavy loads. Because of the 
need for high power for the cylinder and the need for it to extend over a 
substantial distance, compound, double-acting cylinders have had to be 
used and these are complex and expensive to build and assemble. Typical of 
roll clamp designs employing cylinders for this purpose also are disclosed 
in Weinert et al U.S. Pat. No. 4,177,000. 
Lift trucks typically provide tilting of the lift mast several degrees 
forwardly and rearwardly but this is inadequate for providing the desired 
unequal extension of the clamp arm ends necessary for picking up small 
rolls in a horizontal orientation such as when most of the paper on a roll 
has been unrolled (as in printing) and the used up roll must be replaced 
by a fresh roll. See, for example, Quayle U.S. Pat. No. 2,870,929. That 
patent proposed the use of wedge-shaped hangers for mounting the clamp of 
the lift truck mast to support the clamp from a front plate of the lift 
truck, thereby increasing the angle of the clamp arms relative to 
horizontal when the lift truck mast is tipped forward. However, this also 
undesirably displaces the center of gravity forward of the truck, 
resulting in a derating of its capacity. 
Accordingly, it is an object of the present invention to provide a roll 
clamp for lift trucks for lifting rolls or other cylindrical loads which 
permits the clamp arms to be of identical length when the load is to be 
clamped with its axis vertical but which automatically provides for 
skewing of the arms to provide overreaching of the lower arm by the upper 
arm when the clamp arms are rotated for horizontal disposition of the axis 
of the load, and which also then automatically returns the clamp arms to a 
symmetrical position, being no longer skewed, when the clamp arms are once 
more rotated for vertical disposition of the load axis. 
It is another object of the invention to provide such a roll clamp which 
does not cause forward dislocation of the center of gravity of the load 
when the clamp arms are rotated for horizontal load disposition and which 
does not necessitate derating of the lift truck capacity to provide 
overreaching of the upper arm for horizontal disposition of the load. 
An object of the invention is also to provide such a roll clamp for which 
automatic re-orienting and skewing of the arms to a configuration with one 
arm overreaching the other occurs with smooth, low friction, efficient 
operation, requiring relatively little rotation power even when handling 
heavy loads such as paper rolls weighing thousands of pounds. 
It is an object of the invention to provide such a roll clamp which can be 
easily and readily mounted to existing types of lift trucks without 
requiring redesign of same, and which is itself of simple, strong and 
economical construction. 
Briefly, a roll clamp of the invention for being carried by a lift truck 
comprises a rotator including a rear base plate for being mounted upon the 
lift mast of the truck, permitting it to be raised or lowered to a 
vertical position. A frame is gimballed to a front plate of the rotator 
and from this frame extends forwardly a clamp assembly including a pair of 
clamp arms which are swingably disposed, or pivot relative to the frame 
for closing and opening by movement toward and away from each other. The 
rotator is provided for rotating the frame relative to the mast about a 
clamp rotation axis extending forwardly from the mast. Hydraulic cylinders 
serve as power means for selectively opening and closing the arms, which 
have clamp pads at their distal ends for engaging the surfaces of the 
load. The rear base plate of the rotator carries a swash ring defining a 
plane skewed relative to the axis of clamp rotation. The frame includes 
rollers which bear against the ring to cause tilting of the frame relative 
to the rotation axis as the clamp rotates. In this way, the clamp arms 
skew relative to the pivot axis as the base is rotated, automatically 
causing one arm to overextend the other when the clamp arms are in an 
orientation for horizontal load disposition. 
Other objects and features will be in part apparent and in part pointed out 
hereinbelow.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now by reference characters to the drawings and, more 
particularly to FIG. 1, designated generally at A is a lift truck having 
usual lift mast 10 having a carriage 12 which can be raised or lowered by 
the operator to a selected height. Further, mast 10 can be tipped forward 
or backward over a several degree range of movement by a hydraulic 
cylinder or the like, as at 14. Mounted upon carriage 12 is a roll clamp 
of the invention, as designated generally B. 
Roll clamp B is intended for picking up and depositing large paper rolls 
and other large cylindrical loads of the type weighing several thousand 
pounds, or similar cylindrical objects of various diameters. In this 
regard, such rolls may weigh thousands of pounds and may vary greatly in 
diameter. Such loads are intended to be both picked up and deposited with 
the axis of cylindricity either vertical, as when rolls are delivered by a 
commercial vehicle, or horizontal, as when such rolls are dispositioned 
for being placed on a printing press or have been nearly used up and are 
to be removed from the press. The new roll clamp of this invention 
provides automatic skewing of the clamp arms as the roll clamp is rotated 
from the vertical disposition of the load axis to horizontal disposition 
of the axis, causing one arm to automatically overextend the over in the 
latter position but without shifting the center of gravity of the roll 
clamp forward such as would otherwise tend to cause derating of the roll 
clamp and reduce its capability for lifting heavy loads. Such 
overextension allows a roll or other cylindrical load to more readily be 
picked up when it is lying horizontally on a surface. However, as the 
clamp is again rotated for vertical disposition of the roll or load, the 
arms automatically return to an orientation of equal extension, symmetric 
with respect to both the longitudinal axis of the lift truck, and the axis 
of clamp rotation, as is desirable. 
More specifically, roll clamp B has a back plate or base 16 mounted upon 
carriage 12. Referring to FIGS. 2-7, there is carried upon the front 
surface of back plate 16 a conventional rotator, generally 18, having an 
inner race 20 of annular configuration, upon which is journalled an outer 
race 22, there being ball bearings 24 between the races. The outer race is 
provided with teeth 26 around its periphery with which is meshed a worm 
gear 28 driven by a hydraulic motor 30 in either direction under control 
of the lift truck operator. Mounted by a spacer 32 to outer race 22 is a 
front plate 34 of the rotator. The front plate serves as an attachment 
structure for attachment of the clamp proper. 
Plate 34 has at opposite sides a pair of ears 36, 36' having respective 
forwardly extending brackets 38, 38' through which corresponding pivot 
bolts 40, 40' extend for pivotal securement of opposite sides 42, 42' of a 
rectangular frame designated generally 44 which actually carries the clamp 
proper which is designated generally 46. 
Clamp 46 includes a clamp arm mounting frame 48 connected by an extension 
50 otherwise to frame 44. Swingably disposed by pivots 51, 51' at opposite 
sides of frame 48 are a conventional pair of clamp arms 52, 52' moving 
under control of double acting hydraulic cylinders 54, 54'. It is not 
required that these cylinders be of the complex compound type. 
Hingedly connected at the distal ends of arms 52, 52' are respective clamp 
pads 56, 56' configured for closely conformed gripping of the peripheral 
surfaces of a roll or other large cylindrical load, as for example, at 58. 
As will be apparent, cylinders 54, 54' together act to force arms 52, 52' 
toward and away from each other for gripping engagement of roll 58. Also, 
because of their hinged securement, pads 56, 56' may also grip even a very 
small diameter roll, as at 58' in FIGS. 4 and 5. Various conventional 
hydraulic connectors are not shown to simplify the drawings. 
Generally, rotator 18 operates to rotate front plate 34, and thus also 
clamp proper 46, over at least a sector of 90.degree., permitting clamp 
arms 52, 52' to be correspondingly rotated from an orientation shown in 
FIG. 4, wherein the axis of cylindricity of roll 58 is vertical to a 
position as shown in FIG. 5 wherein the axis is horizontal. 
In accordance with the invention, means interengages the base or back plate 
16 and frame 44 for causing frame 44 to rotate about an axis of clamp 
shifting which extends through pivot bolts 40, 40' and on which axis the 
frame 44 is free to pivot or move angularly relative to base plate 16. 
This axis of clamping shifting is perpendicular to the axis of clamp 
rotation resulting from rotational operation of rotator 18. Such axis of 
clamp rotation, as shown in FIGS. 4 and 5, is designated 60. It is 
depicted also in FIG. 6 wherein the axis of clamp shifting, designated 62, 
is seen to be perpendicular therewith. 
More specifically, the means for causing the frame 44 to rotate about axis 
62 as front plate 34 of the rotator turns is constituted by an annular 
swash collar 64 having an inclined outer peripheral surface 66 which 
defines a plane which is inclined relative to base plate by an angle which 
according to the embodiment illustrated is approximately 5.degree., 
thereby providing a normal to the plane which is inclined downwardly and 
then crosses the axis 60 of clamp rotation at a corresponding angle of 
approximately 5.degree.. A greater angle may, of course, be utilized for 
special versions of the new roll clamp. 
The invention contemplates the provision of a follower means for bearing 
against this outer peripheral surface 66 of collar 64. This means 
comprises a pair of rollers 68, 68' carried by the sides of frame 44 which 
extend between sides 42, 42' thereof. For this purpose, the sides of frame 
44 which carry rollers 68, 68' are each comprised of two elongated frame 
members, as at 72a, 72b and 72a', 72b'. The rollers are held captive 
between the respective pairs of frame members by suitable pins 74, 74'. 
Therefore, it will be seen that the rollers roll along the outer surface 
66 of the collar as the frame is turned by rotation of front plate 34, 
causing the frame to rotate about axis 62 and to cause the clamp to shift 
downwardly, as appreciated best in FIG. 5, wherein the clamp is seen to 
include an axis of symmetry 76. This axis may be inclined further 
downwardly by the forward tilting of mast 10 under control of the lift 
truck operator, as shown by the angle .theta. in FIG. 5. 
Thus, as rotator 18 operates, clamp arms 52, 52' rotate from the position 
shown in FIG. 4 to that shown in FIG. 5. In the latter position, the upper 
arm 52' overreaches the lower arm 52 substantially to permit the lower 
clamp pad 56 to reach under a roll, such as that illustrated at 58 or 58', 
regardless of its size and to permit the opposite upper clamp pad 56' to 
oppose the lower clamp pad effectively and, thus, to permit the operator 
to pick up a horizontally disposed roll. This provides extraordinary 
utility of the lift truck when equipped with the new roll clamp. However, 
because the upper arm 52' is not required to be additionally extended, it 
will be seen that the center of gravity of the load, such as roll 58, 
remains the same distance from the clamp arm pivoting frame 48 as it would 
when the roll is dispositioned for vertical handling. This means that the 
lift truck does not need to be derated when rolls are handled in 
horizontal disposition, as has been required with roll clamp handling lift 
trucks of the prior art. 
The new arrangement also makes it possible for the clamp arms to 
automatically shift, producing skewing of axis 76 as the clamp arms turn 
to the position for horizontal disposition of the roll or other load 
without separate operator manipulation of the controls. Similarly also, 
the skewing of the clamp arms is automatically corrected as the clamp arms 
return to the position (as in FIG. 4) with the axis of the load in a 
vertical orientation and wherein it is seen that the axis of symmetry of 
the clamp is coincident with the axis of clamp rotation 60 and so that the 
arms are disposed at opposite sides of the roll clamp assembly by an equal 
distance as is desirable for the handling of rolls and similar large 
cylindrical loads in closed quarters. In this regard, the lift truck can 
approach opposite sides of a tractor trailer, for example, when unloading 
rolls therefrom with equal ease and the operation of the lift truck is not 
thereby disadvantaged by the otherwise asymmetrical placement of clamp 
arms as has been utilized heretofore in the prior art. 
Although the foregoing includes a description of the best mode contemplated 
for carrying out the invention, various modifications are contemplated. 
As various modifications could be made in the constructions herein 
described and illustrated without departing from the scope of the 
invention, it is intended that all matter contained in the foregoing 
description or shown in the accompanying drawings shall be interpreted as 
illustrative rather than limiting.