METHOD AND APPARATUS FOR STRETCHING DOUGH

Abstract: 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 (8) over the surface of dough (12) 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. When moving upstream the roller rotation in the same direction as the movement of the dough , and when moving downstream the roller rotation in the opposite direction.

Description: 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. Bread dough and confectionery dough are plastic materials that in a food manufacturing process are continuously stretched by various stretchers. A known apparatus for stretching dough comprising two conveyors serially disposed and a roller disposed at a fixed position above a downstream conveyor has been preferably used due to its relatively simple mechanism. In this prior art 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 art 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 large 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. Also known from the prior art is EP-A-0173577 which discloses the preamble of claims 1 and 4. This document fails, however, to overcome all the problems of the prior art. The present invention is characterised in that the peripheral speed of the roller is higher than the total of the speed of movement of dough plus the speed of the linear movement of the roller in the upstream direction along said surface of said dough when the roller moves upstream. 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. In a preferred embodiment 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. The invention further extends to an apparatus for working the above-mentioned methods, that comprises a means for rotating a roller when said roller moves upstream at a peripheral speed higher than the total of the speed of the movement of the conveyor plus the speed of the linear movement of the roller, and, preferably, 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 conveyor, and a means for switching the rotational direction of said roller at the upstream and downstream ends of the reciprocating strokes of said roller. The conveying system may comprise a plurality of belt conveyors, roller conveyors or a combination of the two. Some embodiments of present invention will now be described by way of example and with reference to the accompanying drawings, in which:- Fig. 1 is a schematic and side elevation view, partly in section, illustrating a first embodiment of the invention, Fig. 2 is a schematic and side elevation view, partly in section, viewed from behind the apparatus of Fig.1, Fig. 3 is a schematic and side elevation view, partly in section, illustrating a second embodiment of the invention, Fig. 4 is a schematic and side elevation view, partly in section, illustrating a third embodiment of the invention, Fig. 5 is a schematic and side elevation view, partly in section, illustrating a fourth embodiment of the invention, Fig. 6 is a schematic and side elevation view, partly in section, illustrating a fifth embodiment of the invention, and Fig. 7 is a schematic and side elevation view, partly in section, illustrating the apparatus of the prior art. Referring firstly to Fig. 1, an upstream conveyor (2) is driven at speed (D1), and a downstream conveyor (4) is driven at speed (D2), and a rail (22) is horizontally positioned above the conveyors (2,4) and is fixed to a frame (not shown). A slidable cylindrical member attached to the upper end of a bracket (20) is mounted on the rail (22) to slide on the rail (22). The lowermost part of the bracket (20) 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 engagable 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 mm is stretched to a thickness (K) of about 2.5 mm under the following conditions: Speed (D) of the movement of the dough: about 1m/min Diameter of the roller (8): 100 mm Diameter of the first friction wheel (14): 50 mm (ℓ): 100 mm Stroke of the reciprocating movement of the roller (8) : 100 mm The number of the reciprocating movements of the roller (8): 200/min The speed (R) of the linear movement of roller(8): 100 mm X 200=20m/min The peripheral speed of the first friction wheel(14): 20m/min The circumference of the roller (8): 100 mm X 3.14=31.4 cm The circumference of the first friction wheel (14): 50 mm X 3.14=15.7 cm The peripheral speed (P) of the roller (8) when roller (8) moves upstream (20 ÷ 15.7) X 31.4=about 40 m/min The peripheral speed (P) of the roller (8) when the roller (8) moves downstream: 20m/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 1m/min The diameter of the roller (8): 100 mm The peripheral speed of the roller (8): about 1m/min The distance between the roller and the surface of the conveyor: 7 mm. When the original thickness of the dough is about 20mm, the dough entering under the roller can be stretched to the thickness of about 8mm, 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 a 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 a 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 a 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 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), and thus 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 at an angle to the conveyor (4), under the linearly reciprocating area of the roller. 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 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.

Claims: A method of stretching dough (12) comprising rotating a roller (8) over the surface of dough (12) being moved downstream by a conveyor system (1) that includes a series of conveyors, the conveying speed of an upstream conveyor (2) being lower than that of a downstream conveyor (4), said roller (8) being reciprocated upstream and downstream over said surface of said dough (12), and said roller (8) being rotated such that the area of its peripheral surface in contact with the dough (12) moves in the same direction as said dough (12) when said roller (8) moves upstream, and in the opposite direction of said movement of said dough (12) when said roller (8) moves downstream, characterised in that the peripheral speed of said roller (8) is higher than the total of the speed of movement of dough (12) plus the speed of the linear movement of said roller (8) in the upstream direction along said surface of said dough (12) when said roller (8) moves upstream. A method of stretching dough according to claim 1 wherein said roller (8) is reciprocated at a speed higher than the speed of movement of said dough (12) and, wherein the peripheral speed of said roller (8) is equal to or lower than the difference between the speed of the linear movement of said roller (8) and the speed of movement of the dough (12) when said roller moves downstream. A method according to any preceding claim characterised in that the thickness of the dough stretched between said roller (8) and said conveyor system (1) is further regulated by an assisting roller (30) which is disposed above the conveyor (4) at the downstream end of the series of conveyors, said assisting roller (30) being rotated such that the area of its peripheral surface in contact with the dough (12) moves in the same direction as the conveying direction of the dough (12), and the peripheral speed of said assisting roller (30) being the same as the speed of said conveyor at the downstream end (4). Apparatus for stretching dough (12) comprising a roller (8) rotatable about its own axis, a conveyor system (1) arranged below said roller (8) and including at least two serially arranged conveyors, the conveying speed of the upstream conveyor (2) of said conveyors being lower than that of the next downstream conveyor (4), a drive means for reciprocating said roller (8) upstream and downstream over the surface of the conveyor system (1), and a means for rotating said roller (8), characterised in that said rotating means is adapted to rotate said roller (8) at a peripheral speed higher than the total of the speed of movement of the conveyor system (1) plus the speed of the linear movement of the roller (8) when said roller moves upstream. An apparatus as claimed in claim 4 characterised in that means are provided for rotating said roller (8) at a peripheral speed equal to or lower than the difference between the speed of the linear movement of said roller (8) and the speed of movement of the dough (12) when said roller (8) moves downstream, and means are provided for switching the rotational direction of said roller (8) at the upstream and downstream ends of the reciprocating strokes of said roller (8). Apparatus according to claim 5, characterized in that the axle (10) of said roller (8) is provided with a first friction wheel (14) mounted to said axle (10) through a first connecting means (18) that operatively couples said first friction wheel (14) to said axle (10) when said roller (8) moves upstream, and disconnects said first friction wheel (14) from said axle (10) when said roller (8) moves downstream, said first friction wheel (14) being engageable with a first friction plate (16), which first friction plate (16) is fixedly and horizontally mounted to the frame of the apparatus (3), and said axle (10) of said roller is further provided with a second friction wheel (24) mounted to said axle (10) through a second connecting means (28) that operatively couples said second friction wheel (24) to said axle (10) when said roller (8) moves downstream, and disconnects said second friction wheel (24) from said axle (10) when said roller (8) moves upstream, said friction wheel (24) being engageable with a second friction plate (26), which second friction plate (26) is fixedly and horizontally mounted to the frame of the apparatus (3). Apparatus according to claim 4 or 6, characterized in that said means for rotating said roller (8) comprises a built-in reversible motor (34) in said roller (8) to rotate said roller (8) and change the rotational direction of said roller (8). Apparatus according to any of claims 4 to 7 wherein said conveyor system comprises a plurality of belt conveyors. Apparatus according to any of claims 4 to 7 wherein said conveyor system comprises a plurality of roller conveyors . Apparatus according to any of claims 4 to 7 wherein said conveyor system comprises a combination of belt conveyors and roller conveyors.

Inventors: HAYASHI, TORAHIKO
Applicants: RHEON AUTOMATIC MACHINERY CO. LTD.
Application year: 1990
Main classification: A21C3
IPC codes: A21D8, A21C3