Method for stretching dough

A method and apparatus for stretching dough is provided, by which bread dough or confectionery dough is continuously and smoothly stretched by linearly reciprocating a roller over the surface of dough which is continuously conveyed by a series of conveyors, while the roller is rotated by a drive means, and by which method and apparatus the dough can be smoothly stretched without the accumulation of the dough in front of the entrance of the apparatus, thereby obtaining the desired thickness of dough in one operation from the continuously supplied dough material.

BACKGROUND OF THE INVENTION 
1. Field of Invention 
This invention relates to a method and apparatus for stretching dough, and, 
more particularly, to a method and apparatus for stretching plastic 
materials for bread dough or confectionery dough. 
2. Description of Prior Art 
Plastic materials for bread dough or confectionery dough have been 
continuously stretched by various stretchers. Previously an apparatus for 
stretching dough in which two conveyors are serially disposed and a roller 
is disposed at a fixed position above a downstream conveyor has been 
preferably used due to its relatively simple mechanism. In this prior 
apparatus the downstream conveyor is driven faster than the upstream one 
so that the dough is stretched. The roller is rotated at the same 
peripheral speed as that of the conveying speed of the downstream 
conveyor, and in the same direction as that of the dough being conveyed. 
The main function of this prior apparatus depends on the compression by 
the roller of the dough, while the roller is in contact with the surface 
of the dough, and rolls on it. Therefore, the stretching ratio of the 
dough in terms of the thickness of the dough before stretching is small 
compared to the thickness of the dough after stretching, and the tissue of 
the dough tends to be destroyed. Further, when the thickness of the dough 
to be stretched is relatively larger compared to the gap between the 
roller and the surface of the downstream conveyor, frequently the dough 
cannot smoothly advance between the roller and the surface of the 
conveyor, and a substantial part of it stays in front of the roller, which 
results in lowering the manufacturing efficiency. 
SUMMARY OF THE INVENTION 
It is therefore an object of this invention to provide a method of 
stretching dough in which a roller is reciprocated over the surface of the 
dough being continuously conveyed by at least two serially disposed 
conveyors, while the roller is rotated by a drive means. Since the roller 
is reciprocated over the surface of the dough, and the peripheral speed of 
the roller when it moves upstream is higher than the total of the speed of 
the movement of the dough plus the speed of the linear movement of the 
roller, a tangential friction force caused between the surface of the 
dough and the periphery of a roller is generated along the surface of the 
dough, in the downstream direction. Therefore, the dough does not 
accumulate upstream of the roller, and thus smoothly enters the gap 
between the roller and the conveyor, thereby the dough is smoothly 
stretched. 
Another object of this invention is to provide a method of stretching 
dough. The concept of this method is the same as that of the 
above-mentioned method, except that the speed of the linear movement of 
the roller is higher than the speed of the movement of the dough, and the 
peripheral speed of the roller is equal to or lower than the difference 
between the speed of the linear movement of the roller and the speed of 
the movement of the dough when the roller moves downstream. In this method 
the dough is more effectively stretched because the number of 
reciprocations of the roller within a certain period of time increases, 
and the periphery of the roller applies a tangential friction force in the 
downstream direction along the surface of the dough when the roller moves 
downstream. 
Still another object of this invention is to provide an apparatus for 
working the above-mentioned methods, that comprises a means for rotating a 
roller (8) when said roller moves upstream at a peripheral speed higher 
than the total of the speed of the movement of the dough plus the speed of 
the linear movement of the roller, and when said roller moves downstream 
at a peripheral speed equal to or lower than the difference between the 
speed of the linear movement of the roller and the speed of the movement 
of the dough, and a means for switching the rotational direction of said 
roller at the upstream and downstream ends of the reciprocating strokes of 
said roller. 
In one aspect of this invention an apparatus for stretching dough is 
provided that comprises a roller rotatable around its own axis, and a 
conveyor system arranged below said roller and including at least two 
serially arranged conveyors, which can be belt conveyors, and roller 
conveyors or a mixture thereof, the conveying speed of an upstream 
conveyor of said conveyors being lower than that of the next downstream 
conveyor, characterized in that there are provided a drive means for 
reciprocating said roller over the surface of the dough, a means for 
rotating said roller at a peripheral speed higher than the total of the 
speed of the movement of the dough plus the speed of the linear movement 
of the roller when said roller moves upstream, and at a peripheral speed 
equal to or lower than the difference between the speed of the linear 
movement of the roller and the speed of movement of the dough when said 
roller moves downstream, and a means for switching the rotational 
direction of said roller at the upstream and downstream ends of the 
reciprocating strokes of said roller.

PREFERRED EMBODIMENTS OF THE INVENTION 
The first embodiment of this invention will now be described by reference 
to the drawings. In FIG. 1 an upstream conveyor (2) that is driven at 
speed (D1), and a downstream conveyor (4) that is driven at speed (D2), 
and a rail (22) horizontally positioned above the conveyors (2,4) and that 
is fixed to a frame (not shown), are arranged. A slidable cylindrical 
member attached to the upper end of a bracket (20) is mounted on the rail 
(22) to slide on it. The lowermost part of it is connected to the axle 
(10) of a roller (8). The bracket (20) is adapted to reciprocate over a 
distance (l) by a crank mechanism (not shown), so that the roller (8) can 
reciprocate over the distance (l) at a speed (R) in the linear direction. 
A first cam clutch (18) is mounted on the axle (10), and a first friction 
wheel (14) is mounted on the first cam clutch (18). The first friction 
wheel has a diameter smaller than the roller (8). The first cam clutch 
(18) can operatively couple the first friction wheel (14) to the axle (10) 
when the roller (8) moves upstream in the direction indicated by an arrow 
(A), and can disconnect said first friction wheel (14) from said axle (10) 
when said roller (8) moves downstream. The first friction wheel (14) is 
engageable with a first friction plate (16) that is fixedly and 
horizontally mounted to the frame (not shown) of an apparatus (3). When 
the roller (8) linearly moves upstream by the crank mechanism, the roller 
(8) is rotated in the direction indicated by an arrow (a). Dough (12) that 
has a thickness (S) is conveyed on the conveyors (2). The dough (12) on 
the conveyor (2) is moved at approximately the same speed as speed (D1), 
and the dough (12) on the conveyor (4) is moved at approximately the same 
speed as speed (D2). However, since speeds (D1) and (D2) differ from each 
other in stretching the dough, the speed of the movement of the dough 
varies at various positions on the conveyors (2,4). Therefore, it is 
assumed here that the movement of the dough (12) under an area that the 
roller (8) is reciprocated has an average speed of (D). The peripheral 
speed (P) of the roller (8) depends on the diameter of the first friction 
wheel (14), provided that other conditions, for example, the speed (R) of 
the linear movement of the roller (8), the diameter of the roller (8), and 
so forth, are assumed as constant. When the peripheral speed (P) of the 
roller (8) that is rotated in the direction indicated by an arrow (a) is 
equal to the total of the speed (D) of the movement of the dough plus the 
speed (R) of the linear movement of the roller (8), the roller (8) rolls 
on the surface of the dough (12), and does so generally without any 
friction being generated between the periphery of the roller (8) and the 
surface of the dough (12). When the roller (8) rolls on the surface of the 
dough, the length of travel of a certain point on the periphery of the 
roller (8) due to its rolling is about the same as the distance (l). In 
this case no frictional force in the direction of movement is applied by 
the periphery of the roller (8) to the surface of the dough (12). However, 
when the peripheral speed (P) of the roller (8) is higher than the total 
of the speed (D) of the movement of the dough plus the speed (R) of the 
linear movement of the roller (8), the rotational loci of the 
circumference of the roller (8) are longer than the case where the roller 
(8) rolls on the surface of the dough without frictional force being 
generated between the periphery of the roller (8) and the surface of the 
dough. Therefore, the periphery of the roller (8) applies a tangential 
frictional force in the downstream direction along the surface of the 
dough (12), while the roller (8) is moved upstream, and the portion of 
dough at its surface is compelled to be pushed downstream. The speed (R) 
of the linear movement of the roller may preferably be higher than the 
speed (D) of the movement of the dough, so that a large number of 
reciprocating movements of the roller can more smoothly stretch the dough. 
In contrast, in the apparatus of the prior art shown in FIG. 7, dough (12) 
that has a thickness (S) that is larger than the gap between the roller 
and the surface of the conveyor may not always pass the roller (8) without 
leaving behind a substantial amount of dough, which flows along an arrow 
(F), thereby accumulating in front of the roller (8). 
FIG. 2 shows the apparatus of the first embodiment viewed from behind the 
apparatus of FIG. 1. In FIG. 2, the axle (10) of said roller (8) is 
further provided with a second friction wheel (24) that has a diameter 
somewhat larger than that of the roller (8), and said second friction 
wheel (24) is mounted to said axle (10) through a second cam clutch (28). 
The second cam clutch (28) can operatively couple the second friction 
wheel (24) to the axle (10) when said roller (8) moves downstream, and can 
disconnect the second friction wheel (24) from the axle (10) when the 
roller (8) moves upstream. The friction wheel (24) is engageable with a 
second friction plate (26) fixedly and horizontally mounted to the frame 
(not shown) of the apparatus (3). When the roller (8) linearly moves 
downstream in the direction indicated by an arrow (B), the roller (8) is 
rotated in a direction indicated by an arrow (b). When the peripheral 
speed (P) of the roller (8) that is rotated in a direction indicated by an 
arrow (b) is equal to the difference between the speed (R) of the linear 
movement of the roller (8) and the speed of the movement of the dough when 
the roller (8) moves downstream, the roller (8) rolls on the surface of 
the dough (12), and does so generally without any friction being generated 
between the periphery of the roller (8) and the surface of the dough (12). 
Since the second friction wheel (24) has a diameter somewhat larger than 
that of the roller (8), the peripheral speed (P) of the roller (8) is 
lower than the difference between the speed (R) of the linear movement of 
the roller (8) and the speed of movement of dough when the roller (8) 
moves downstream, the periphery of the roller (8) applies a tangential 
frictional force in the downstream direction along the surface of the 
dough (12), while the roller (8) is moved downstream, to compel the 
portion of dough at its surface to be pushed downstream. If the speed (R) 
of the linear movement of the roller (8) is equal to the speed (D) of the 
dough when the roller (8) moves downstream, the roller (8) stays at a same 
position on the surface of the dough (12), while the roller (12) linearly 
moves together with the dough. The crank mechanism can be replaced with 
other suitable drive means (not shown). In this case, the periphery of the 
roller (8) applies a tangential frictional force in the upstream direction 
along the surface of the dough (12). Therefore, the speed (R) of the 
linear movement of the roller (8) is preferably higher than the speed (D) 
of the movement of the dough (12), when the roller (8) moves downstream. 
When the roller (8) moves upstream, the speed (R) of the linear movement 
of the roller (8) may also be higher than the speed (D) of the movement of 
the dough (12). 
Thus, the dough (12) is smoothly stretched by reciprocating the roller over 
its surface, while the roller (8) is rotated, without the accumulation of 
the dough (12) in front of the roller (8). In this embodiment dough that 
has a thickness of about 20.sub.mm is stretched to a (K) of about 
2.5.sub.mm under the following conditions: 
Speed (D) of the movement of the dough: about 1.sub.m /min 
Diameter of the roller (8): 100.sub.mm 
Diameter of the first friction wheel (14): 50.sub.mm 
(l): 100.sub.mm 
Stroke of the reciprocating movement of the roller (8): 100.sub.mm 
The number of the reciprocating movements of the roller (8): 200/min 
The speed (R) of the linear movement of roller (8): 100.sub.mm 
.times.200=20.sub.m /min 
The peripheral speed of the first friction wheel (14): 20.sub.m /min 
The circumference of the roller (8): 100.sub.mm .times.3.14=31.4.sub.cm 
The circumference of the first friction wheel (14): 50.sub.mm 
.times.3.14=15.7.sub.cm 
The peripheral speed (P) of the roller (8) when roller (8) moves upstream: 
(20.div.15.7).times.31.4=about 40.sub.m /min 
The peripheral speed (P) of the roller (8) when the roller (8) moves 
downstream: 20.sub.m /min (the roller rolls on the surface of the dough 
without generating any friction between the periphery of the roller and 
the dough) 
In contrast, in the apparatus of the prior art as shown in FIG. 7, 
conditions for the operation are as follows: 
The speed of the movement of the dough: about 1.sub.m /min 
The diameter of the roller (8): 100.sub.mm 
The peripheral speed of the roller (8): about 1.sub.m /min 
The distance between the roller and the surface of the conveyor: 7.sub.mm 
When the original thickness of the dough is about 20.sub.mm, the dough 
entering under the roller can be stretched to the thickness of about 
8.sub.mm, and a substantial amount of dough may stay upstream of the 
roller unless a complicated mechanism is designed to avoid the bulging of 
dough upstream of the roller. Further, the apparatus of the prior art 
cannot stretch the dough to a thickness comparable to that of the 
stretched dough of this invention. 
FIG. 3 shows the second embodiment of this invention, where a roller 
conveyor (1) that comprises a plurality of rollers (6) is disposed between 
two belt conveyors (their main parts are not shown). The conveying speeds 
of these conveyors differ, the conveying speed of the next downstream 
conveyor being in turn higher than that of the preceding conveyor. A 
series of conveyors for use in this embodiment may be composed of a 
plurality of belt conveyors, of a plurality of roller conveyors, or of a 
plurality of conveyors that include one or more belt conveyors and one or 
more roller conveyors. By this apparatus of FIG. 3 the dough (12) is as 
smoothly stretched as the dough (12) is stretched in the first embodiment. 
FIG. 4 shows the third embodiment of this invention, where an assisting 
roller (30) is further disposed above the conveyor (4) of the apparatus 
(3) of the first embodiment. The thickness of the dough stretched by the 
roller (8) and the conveyors (2, 4) tends to somewhat increase when the 
dough has a relatively high elasticity. Therefore, to avoid such an 
increase in the thickness of the dough the dough is further regulated by 
the assisting roller (30), which is preferably disposed at the downstream 
end of the series of conveyors. The assisting roller (30) is rotated in 
the same direction as the conveying direction of the dough (12), and the 
peripheral speed of the assisting roller (30) is the same as the speed of 
the conveyor at the downstream end (4). 
FIG. 5 shows the fourth embodiment of this invention, where a device for 
rotating the roller (8) is a built-in reversible motor (34), and a device 
for reciprocating the roller (8) comprises a servomotor (38), a crank 
shaft (36), and a crank (35). One end of the crank (35) is linked through 
a crank pin to a crank arm that is connected to the crank shaft (36). The 
other end of the crank (35) is linked through a pin to the uppermost part 
of the bracket (20). The roller (8) can be reciprocated by actuating the 
servomotor (38), at any desired speeds of the linear movement of the 
roller. The peripheral speed (P) of the roller (8) can be controlled by 
changing the frequency of the power source for the built-in reversible 
motor (34). The motor shaft (32) of the built-in in reversible motor (34) 
is connected to the lowermost part of the bracket (20). The roller (8) is 
reciprocated over a distance (l) by the crank (35), while it is rotated by 
the built-in reversible motor (34). A sensor (42) is disposed above the 
rail (22) and at the upstream end of the reciprocating strokes of the 
roller (8). The sensor (42) can detect the arrival of the bracket (20) at 
the upstream end of the reciprocating strokes of the roller (8), and send 
to the built-in reversible motor (34) a signal to change the rotational 
direction of the built-in reversible motor (34), namely the roller (8), to 
a direction indicated by an arrow (b). A sensor (40) is disposed above the 
rail (22) and at the downstream end of the reciprocating strokes of the 
roller (8). The sensor (40) can detect the arrival of the bracket (20) at 
the downstream end of the reciprocating strokes of the roller (8), and 
send to the built-in reversible motor (34) a signal to change the 
rotational direction of the built-in reversible motor (34), namely the 
roller (8), to a direction indicated by an arrow (a). In the apparatus of 
this embodiment, the peripheral speed (P) of the roller (8) can be changed 
during its reciprocating movement to meet the conveying speed of the 
dough, independently of the speed of the linear movement of the roller. By 
the apparatus of this embodiment, the dough (12) is as smoothly stretched 
as the dough (12) is stretched in the first embodiment. 
FIG. 6 shows the fifth embodiment of this invention, where the conveying 
surface of the conveyor (2) is inclined against that of the conveyor (4), 
under the linearly reciprocating area of the roller, to make an angle. In 
this embodiment, since the form of the portion of the dough under the 
linearly reciprocating area of the roller is tapered, the stretching is 
more smoothly attained. Also, in place of inclining the conveyor (2), the 
loci of the linear movement of the roller (8) may be inclined against the 
straight conveying surface formed by the series of the conveyors. For 
example, in FIG. 6 the rail (22) may be inclined so that the vertical 
position of the uppermost part of the bracket (20) at the upstream end of 
the reciprocating strokes may be raised. 
As described above, the method and apparatus for stretching dough of this 
invention can smoothly stretch the dough without the accumulation of the 
dough in front of the entrance of the apparatus, thereby obtaining the 
desired dough thickness in one operation from the continuously supplied 
dough material. These advantages are due to the rotation of the roller, 
while it is being reciprocated over the surface of the dough being 
continuously conveyed which applies to the dough the tangential force of 
the roller that is caused by the friction between the periphery of the 
roller and the surface of dough, along the surface of the dough. Further, 
since the contact portion of the roller with the surface of dough quickly 
changes due to the rotational and linear movements of the roller, the 
amount of the flour sprinkled onto the surface of dough to avoid the 
adhesion of the dough to the surface of roller is remarkably decreased, 
compared to the apparatus of the prior art. In conclusion, the simplified 
method and apparatus of this invention can increase stretching dough 
efficiency without using any large-scale apparatus, and can achieve low 
production costs.