Methods for handling sheet material

In the feeding of sheet material to a machine such as a tire building former a sheet is first placed on a table and one edge of the sheet is aligned with a first datum line, preferably by tilting the table and supplying floatation air under the sheet. The sheet is then picked up and moved transversely through a predetermined distance by a gripping device to align the edge with a second datum line so as to enable the sheet to be fed in appropriate alignment to a machine.

This invention relates to methods and apparatus for handling sheet maerial, 
particularly but not exclusively for use in the manufacture of pneumatic 
tires. 
In the manufacture of pneumatic tires it is necessary to wrap sheets of 
material such as plies of rubberized parallel-cord fabric around a tire 
building former, and in order to obtain a uniform tire structure it is 
essential to feed the plies along an accurately predetermined path in 
presenting them to the former. It is also important that the lenth of each 
ply and the circumference of the former are accurately matched so as to 
achieve a good joining relationship of the ends of the ply after it has 
been wrapped aroudn the former. These requirements are particularly 
difficult to satisfy in the practice of automatic methods of tire 
building. 
One object of the present invention is to provide a method of feeding a 
sheet of ply material to a tire building former in which the alignment of 
the ply is accurately determined, and a second object is to match 
accurately the length of the ply and the circumferential dimension of the 
former and any material already on the former. 
According to one aspect of the invention, a method of feeding a sheet of 
material to a machine comprises laying the sheet on a table, arranging the 
sheet on the table to align an edge of the sheet with a first datum line, 
applying a gripping device to the sheet and moving the gripping device and 
the sheet in an alignment-preserving manner automatically to align the 
said edge with a second datum line bearing a predetermined relationship to 
the first datum line and suitably positioned in relation to the said 
machine to enable the sheet to be fed in appropriate alignment to the 
machine. 
In a preferred method in accordance with the invention the sheet of 
material is a ply of tire building fabric and the machine is a tire 
building former. The alignment of a side edge of the ply with a first 
datum line on the table is preferably carried out, according to a further 
feature of the invention, by transversely tilting the table while 
providing a flow of air beneath the ply to permit it to float over the 
table surface into appropriate alignment, against a raised side abutment. 
Additionally, an end abutment may be provided, the associated ply end 
being moved into contact with the end abutment by longitudinally tilting 
the table while providing a flow of floatation air beneath the ply. 
Following the accurate placing of a ply on a table, the ply may be moved 
transversely, for example by a vacuum gripping device, and positioned on a 
conveyor so that its position and alignment on the conveyor bears a fixed 
relationship to the position and alignment which has beene stablished on 
the table. This position and alignment is arranged so that the conveyor 
may then be operated to feed the ply in accurate position and alignment to 
a tire building former suitably located adjacent the conveyor. 
In order to match the length of the ply and the circumference of the former 
so as to achieve a good joining relationship of the ends of the ply after 
it has been wrapped around the former, means may be provided to measure 
accurately the length of each ply and to adjust the diameter of the former 
if required. 
The invention also provides apparatus for carrying out the method in 
accordance with the invention, comprising a table, means for tilting the 
table and for supplying floatation air to its surface so as to enable a 
sheet of material on the table to be aligned with the edge of the sheet in 
alignment with a first datum line, and a gripping device for the sheet 
arranged to be movable in an alignment-preserving manner automatically to 
align the said edge with a second datum line bearing a predetermined 
relationship to the first datum line so as to enable the sheet to be fed 
in appropriate alignment to a machine. 
In a preferred apparatus in accordance with the invention the machine is a 
tire building former.

In the manufacture of a radial-ply pneumatic tire the carcass of the tire 
includes a ply of parallel-cord rubberized fabric in which the cords are 
arranged to run parallel to the axis of a tire building former. In the 
operation of building a tire in accordance with the method described in 
United Kingdom Application Publication No. 2,129,380 dated May 16, 1984 a 
pair of tire bead elements are located coaxially at opposite ends of a 
bead tube in axially spaced relationship and an expansible former around 
which tire carcass material is wrapped is located coaxially within the 
tube in a predetermined position so that the tire carcass material 
projects axially beyond the bead elements at each end of the former, the 
former then being expanded to cause the carcass to contact the bead 
elements and to turn the projecting ends of the material radially 
outwardly around the bead elements. 
In order to carry out this process it is necessary for a ply of carcass 
material and an inner lining of rubber to be wrapped around the expandible 
former in a predetermined axial position on the former and with the cords 
of the ply in axial alignment. It is also necessary, particularly when the 
operation is carried out by automatic means, that when the ply is wrapped 
around the former its ends meet in a relationship which is nearly exactly 
abutting. 
In order to achieve the accurately predetermined location of the ply in the 
axial sense relative to the former, a method as illustrated in the 
accompanying drawings is operated as follows: 
FIG. 1 and FIG. 6 show a floatation table 10 in a state where a ply 11 has 
been placed in position on the table by a vacuum-operated gripping device 
12 which is movable along an overhead track 13 (see FIG. 11) to transfer 
the ply from a temporary storage tray (not shown) to the floatation table. 
The cords of the ply are roughly aligned parallel with the shorter sides 
of the table 10. 
The floatation table 10 is mounted on a sub-frame 15 by means of a ball 
joint 16 at one corner and by open location socket hinge joints 17, 18, 19 
at the remaining three corners. The joints 17 to 19 each comprise a 
semi-cylindrical member 20 (see FIG. 6) secured tot he table, which 
engages a corresponding socket 21 secured to the sub-frame 15 to permit 
tilting of the table about the axis of the member 20 while permitting the 
component parts of the joint to separate when required, e.g. as shown in 
FIG. 7 where the joint 17 is illustrated in the separated position. 
The arrangment of the table 10 is such that it may be tilted about a 
longitudinal axis through the joints 16 and 17 so as to move the ply 11 
transversely to the right as shown in FIGS. 1 and 2, and it may also be 
tilted about a transverse axis through the joints 16 and 19 to move the 
ply longitudinally as shown in FIG. 3. The table 10 is provided with a 
porous upper surface communicating with suitable ducts below the surface 
through which compressed air may be supplied to provide floatation of the 
ply, enabling it to move easily over the table surface in whichever 
direction the table is tilted. 
A datum line defined by spring-loaded pegs 23, 24, 25 is provided on the 
table to constitute a first datum line for the ply, and similar pegs 26,27 
provide an abutment for positioning the forward edge of the ply. Alignment 
of one edge of the ply with the first datum line is achieved as shown in 
FIGS. 2 and 7 by tilting the table and supplying air floatation to the 
underside of the ply. The tilting of the table is achieved by a pneumatic 
ram engaging the underside of the table at a lift point 28 which is offset 
from the centre of the table so as to produce initially a tilt about an 
axis through the joints 16,17, and an intermediate stop in the form of a 
stirrup 30 attached to the table at its upper end is positioned so that 
when the lower end 31 of the stirrup engages a suitable abutment (not 
shown) beneath the table, as seen in FIG. 7, the axis of tilt of the table 
is transferred to a line through joints 16,19. The relationship between 
the point 28 at which the lifting ram applies its thrust and the position 
of the intermediate stop 30 is such as to cause the table to tilt first 
about a diagonal axis through the joints 16,18, until the joint 19 is 
reengaged and then to continue tilting about the transverse axis through 
the joints 16 and 19 as shown in FIG. 8. 
After the tilting action illustrated in FIG. 8 has been completed, the 
forward end edge 35 of the ply 11 will have moved into engagement with the 
pegs 26,27, thus locating the ply in a predetermined position both with 
respect to its side edge 36 and its forward end edge 35. In this position, 
the air floatation of the ply is terminated so that the ply settles into a 
resting position on the table, as illustrated in FIGS. 9 and 10. The table 
is then lowered slowly until it is horizontally disposed, thus preserving 
the accurate location of the ply. 
As shown in dotted lines in FIG. 11 the gripping device 12 is located in a 
predetermined position above the table 10 and carries photo-electric cells 
40-43. The photo-elective cells 40-43 are connected in an electrical 
control system, providing data which confirms that the position of the ply 
as shown in FIGS. 4 and 5 is in fact in the correct predetermined location 
and alignment. The gripping device may then be operated so as to pick up 
the ply by means of a vacuum suction device (not illustrated) and hole the 
ply in a flat condition against the underside of a flat shoe 50 of similar 
area to the table 10. 
The gripping device 12 is then moved to the full-line position shown in 
FIG. 11 above a conveyor 55, holding the edge 36 of the ply in alignment 
with a second datum line (not shown), parallel to the first datum line, 
which is arranged to have an accurately predetermined relationship with a 
tire building former 56. Adjustable stops 60,61 are provided to enable the 
relationship of the positions of the gripping device 12 adjacent the table 
10 and the building former 56 respectively to be accurately predetermined, 
thus determining the position of the second datum line in relationship to 
the building former. The gripping device 12 is then operated to deposit 
the ply 11 on the conveyor 55 without disturbing its location and 
alignment. 
After the gripping device 12 has been disengaged from the ply 11, leaving 
it on the conveyor 55, the position of the ply is again checked by the 
photo-electric cells 40-43. The conveyor 55 comprises an endless belt 65 
passing around fixed rollers 66,67,68,69,70 and a movable roller 71 which 
can tighten the belt in lapping relationship with the former 56 as shown 
in FIG. 12 and which can be lowered to release the belt from the former to 
enable the former to be withdrawn from the conveyor after a ply 11 has 
been transferred to it. Means is provided for driving the belt so that its 
upper run moves towards the former carrying the ply around the former so 
that it adheres to the surface of a rubber inner lining which has already 
been applied to the former 56 at a previous stage of the tire building 
process. 
The photo-electric cells 43 and 40 are spaced apart at an accurately 
predetermined distance and are arranged to provide signals to a control 
system as the leading end 35 and the trailing end 75 of each ply 11 passes 
the photo-electric cells 43 and 40 respectively, the control system 
including a rotary encoder driven from the belt surface so that a 
measurement of the length of the ply 11 may be determined before the ply 
has been wrapped around the former 56. Means (not illustrated) is provided 
for controlling and adjusting the diameter of the former 56, which may be 
of the type incorporating radially movable segments under the control of a 
motor-driven expander mechanism so as to match the circumference of the 
former and any material carried thereon (i.e. a rubber liner) to the 
length of the particular ply which is being fed to it. By this means, it 
is possible to achieve a good joint between the ends of the ply when it 
has been fully transferred to the former. 
The method and appartatus described above has the advantage that it enables 
sheets of parallel-cord ply material to be fed in an accurately 
predetermined location with one edge in accurate alignment with a 
predetermined circumferential line around the building former 56 as 
determined by the position of the adjustable stop 61. 
Should the ply be of dimensions or shape which are outside the permitted 
tolerances, this can be detected by the photo-electric cells 40-43 and the 
ply can be rejected, for example by reversing the conveyor 53. 
While in the specific example described above the invention is applied to 
the handling of ply fabric for pneumatic tire carcasses, it may also be 
used for handling other tire building components, or components for 
incorporation into other products of the rubber industry such as 
suspension bellows, or any other industrial applicaiton where sheet 
material is required to be fed in accurate relationship to a machine. The 
component may have a not-rectangular shape, such as a bias-cut ply and in 
this case one side edge is aligned as described above, and the leading 
edge may be positioned against a single abutment.