Method and apparatus for stretching dough

Abstract: A method for producing a dough sheet (2) having a predetermined width and height from a dough mass (1) of a non-uniform volume, comprising the steps of compressing the mass on a supplying conveyor (3), detecting any change of width of the compressed dough sheet, driving a delivery conveyor (4) provided downstream of the supplying conveyor (3) at a constant speed, while changing the speed of the supplying conveyor (3), and, further, stretching the dough sheet (2) on the delivery conveyor (4), the supplying conveyor (3) being driven based on the data of any detected change in the dough width. Apparatuses are provided to carry out the above method.

Description: This invention relates to a method and apparatus for stretching a plastic material, and, more particularly, to a method and apparatus for stretching dough for bread or confectionery. The prior art related to the stretching of dough of this invention is disclosed in U.S. Patent Nos. 4,692,110 and 4,631,021. U.S. Patent No. 4,692,110 discloses a dough-stretching apparatus whose object is to stretch a mass of supplied dough into a sheet of dough having a predetermined thickness. However, this apparatus is neither capable of making the width of the stretched sheet of dough uniform, nor of producing the stretched sheet of dough at a constant production speed. U.S. Patent No. 4,631,021 discloses an apparatus for producing a sheet of dough having predetermined dimensions and delivering it at a predetermined delivery rate to produce a sheet of dough having a uniform shape. However, the proposed means is based on the measurement of the weight of a mass of dough supplied in an indefinite shape before the stretching step. From EP-A-0 197 671, it is known to provide a method for continuously compressing a supplied mass of a non-uniform volume per unit length of dough into a dough sheet of a uniform volume per unit length, comprising the steps of: conveying the supplied mass of the non-uniform volume of dough on a supplying conveyor to a delivery conveyor located downstream of the supplying conveyor, compressing the mass of dough on the supplying conveyor into a dough sheet having a uniform thickness, and stretching the dough on the delivery conveyor. The present invention is characterised by detecting the dough width at the point where the dough is compressed, and setting the speed of the supplying conveyor relative to the speed of the delivery conveyor, based on the detected value of the dough width. From EP-A-0 197 671 it is known to provide a dough-stretching apparatus comprising: a dough-supplying conveyor for conveying a continuous sheet of dough and a delivery conveyor positioned in series with and downstream of the supplying conveyor, a compressing means for applying pressure to the dough, disposed at the downstream end of the supplying conveyor. The present invention is characterised by a dough-width measuring device located near the compressing means connected to a means for controlling the relative speed of the supplying conveyor and the delivery conveyor, and the dough-width measuring device and control means being adapted so as to measure the width of the dough when it is compressed by the compressing means and to change the speed of the supplying conveyor relative to the delivery conveyor in relation to the measured dough width before it is supplied onto the delivery conveyor, so as to produce a dough sheet of a uniform width and thickness. This invention thus provides an automatic dough-stretching apparatus which produces a continuous sheet of dough used for the production of bread and confectionery and in which the manufacturing parameters, including the production speed, width, and thickness of the sheet of dough, are preferably previously stored in a computer memory, so that a mass of dough supplied with a non-uniform width or thickness can be automatically stretched into a sheet of dough that satisfies the conditions stored in the computer memory. The dough-stretching apparatus of the present invention includes a compressing means located above a dough-supplying conveyor so as to make uniform the height of a mass of dough supplied in an indefinite shape. When the height of the mass of the supplied dough is made uniform, the only variable in the dimensions of the stretched sheet of dough will be its width. Therefore, by merely continuously measuring the width of the sheet of dough passing through a measuring position, the volume of portions of the dough sheet at that position can be continuously or sequentially recorded in the computer memory. Based on the volume data stored in the memory, the speed of the dough-supplying conveyor may be suitably and continuously changed so that the amount of the sheet of dough transferred per unit time from the dough-supplying conveyor onto a constant speed delivery conveyor is made uniform. Preferably the compressing means comprises one or a plurality of rollers located above and adjacent the area between the downstream end of the supplying conveyor and the upstream end of the delivery conveyor, the roller or rollers reciprocating over a predetermined range while rolling along the moving path of the two conveyors. In preferred embodiments a plurality of freely rotatable rollers are provided spaced apart from each other and from the conveyors and above the area between the downstream end of the supplying conveyor and the upstream end of the delivery conveyor, the rollers orbiting above said area, the dough being supplied into the space between the rollers and the upper surface of the supplying conveyor and causing the rollers to rotate by friction with the dough sheet. Preferred embodiments of the present invention will now be described by way of example only and with reference to the attached drawings, in which: Fig. 1 is a schematic side elevational view of a first embodiment of the apparatus of the present invention; Fig. 2 is a top plan view of the embodiment shown in Fig. 1; Fig. 3 shows a schematic cross section of the apparatus taken along the line 3-3 in Fig. 1; Fig. 4 is a schematic side elevational view of a second embodiment of the apparatus of the present invention; Fig. 5 is a schematic side elevational view of a third embodiment of the apparatus of the present invention; Fig. 6 is a schematic top plan view of those apparatuses shown in Figs. 4 and 5; Fig. 7 is a schematic side elevational view of a fourth embodiment of the apparatus of the present invention; Fig. 8 is a schematic side elevational view of a fifth embodiment of the apparatus of the present invention; and Fig. 9 schematically illustrates a rotation input mechanism that actuates the reciprocating rollers shown in Fig. 7. A mass of dough 1 with an indefinite shape is placed on a dough-supplying conveyor 3. Downstream of the supplying conveyor 3 is positioned a delivery conveyor 4. A dough-compressing means in the form of a dough feed roller 5 is positioned at the downstream end of and above the supplying conveyor 3, spaced apart from the conveying path of the supplying conveyor 3 by a predetermined distance, T₁. In Fig. 1, two distance sensors 11 are disposed, one on each side of the conveying path of the conveyor 3 and near the roller 5 at a width-measuring position. The distance sensors 11 sense the distance between the respective sides of the mass of dough 1, and send signals representing the distance to a computer 12 (Fig. 7) which computes the width W₁ (Fig. 2) of the mass of dough 1. The dough-feed roller 5 compresses and makes the height of the dough 1 uniform. The sectional area S (Fig. 3) of the mass of dough 1 at the width-measuring position is given by the formula S = W₁ X T₁ , wherein T₁ is the height of the dough under the roller 5. The computer 12 thus computes the sectional area S of the mass of the dough 1 at the width-measuring position according to the equation W₁ X T₁ = S . Then, on the basis of the computed value of the sectional area S, the computer 12 computes the desired speed V₁ for the dough-supplying conveyor 3 and sends signals to a servomotor 13 (Fig. 7) to control its rotation. The servomotor 13 thus adjusts the speed V₁ of the conveyor 3. A compressing means such as, for example, the shaping roller 6, is located above the delivery conveyor 4. The roller 6 reduces the thickness of the dough to T₂. The data representing the desired width W₂ (Fig. 2) and thickness T₂ of the dough sheet 2 to be produced are stored, together with the data representing the desired production speed V₂, in the memory of the computer 12. The dough-stretching operation is carried out while the speed of the delivery conveyor 4 is maintained at the value V₂. The computer 12 continuously controls the speed V₁ of the dough-supplying conveyor 3 so as to satisfy the following relation: T₂ X W₂ X V₂ = T₁ X W₁ X V₁ Due to the speed difference between the dough-supplying conveyor 3 and the delivery conveyor 4, a dough sheet 2 having the desired thickness T₂ and the desired width W₂ can be produced. The apparatus of the second embodiment of the present invention, shown in Fig. 4, features a single roller. That is, the reciprocating roller 7 acts as both the compressing means to make the height of the mass of dough 1 uniform so that it has the value T₁ and the means for controlling the thickness T₂ of the stretched sheet of dough 2 of the first embodiment. The reciprocating roller 7 repeats its reciprocating movement while rolling over an illustrated range ℓ. The range ℓ includes a range A between the upstream operating limit of the roller 7 and the downstream end 3' of the dough-supplying conveyor 3, and a range B between the downstream operating limit of the roller 7 and the upstream end 4' of the delivery conveyor 4. Thus the roller flattens the upper surface of the mass of dough 1 having the indefinite shape, controls the dough thickness T₁ at a width-measuring position on the dough-supplying conveyor 3, and controls the dough thickness T₂ on the delivery conveyor 4. In Fig. 4, the position of the downstream end 3' of the dough-supplying conveyor 3 is selected to be higher than the upstream end 3'' of the conveyor 3. The purpose of this structure is to greatly enhance the effect of compressing and shaping the dough by the operation of the roller 7 that reciprocates while it rolls. Namely, since the dough-supplying conveyor is inclined relative to the delivery conveyor, the mass of dough can smoothly enter the space between the roller 7 and the conveyor 3, and the dough can be easily and effectively flattened. The distance sensors 11 senses the width W₂ of the mass of dough 1. The sectional area S of the mass of dough 1 at the width-measuring position can be expressed as S = T₁ X W₁ . Further, the controlled speed V₁ of the dough-supplying conveyor 3 relative to the constant speed V₂ of the delivery conveyor 4 is calculated according to the following equation: T₂ X W₂ X V₂ = T₁ X W₁ X V₁ where T₁ is a constant, W₁ is a variable, and V₁ is a variable determined by the value of (T₁ X W₁). Based on the above equation, the computer 12 (Fig. 7) controls the rotating speed of the servomotor 13 which drives the conveyor 3 to attain the desired control. A third embodiment of the present invention is shown in Figs. 5 and 6. The apparatus shown in Figs. 5 and 6 is a modification of that shown in Fig. 4 in that the dough-supplying conveyor 3 is disposed in the horizontal direction at a level lower than the level of the delivery conveyor 4. In the fourth embodiment of the present invention, shown in Fig. 7, the apparatus has two linked reciprocating rollers 8 and 9 that are arranged so that the reciprocating roller 8 substantially reciprocates over a range ℓ ₁ above the dough-supplying conveyor 3 and a part of the delivery conveyor 4, while the reciprocating roller, 9 reciprocates over a range ℓ ₂ above the delivery conveyor 4. By this arrangement, the reciprocating roller 9 rotates so that its peripheral speed is equivalent to the speed V₂ of the delivery conveyor, while the roller 8 rotates so that its peripheral speed is equivalent to the speed, V₁ of the dough-supplying conveyor 3. The computer 12 controls the rotating speed of the servomotor 13 to drive the conveyor 3 in accordance with the above described control relation. Fig. 9 shows a rotation input mechanism for the reciprocating rollers 8 and 9 of Fig. 7. A chain 14 is arranged to be driven in the same direction and at the same speed as is the delivery conveyor 4. A sprocket 9' meshing with this chain 14 is mounted on one end of the shaft of the roller 9. A crank 16 and a rod 15 are driven to cause a reciprocating movement of the sprocket 9' engaging the chain 14, so that the roller 9 reciprocates over the range ℓ ₂ while rolling. Another sprocket 8' is mounted on one end of the shaft of the reciprocating roller 8 and also engages the chain 14, so that the roller 8 similarly reciprocates over the range ℓ ₁ while rolling. In this case, the diameter of the sprocket 8' is selected to be larger than that of the sprocket 9', so that the peripheral speed of the sprocket 8' is lower than that of the sprocket 9'. Therefore, when the rollers 8 and 9 have the same diameter, the roller 8 rolls so that its peripheral speed becomes the same as the speed of the mass of dough 1 being conveyed by the dough-supplying conveyor 3, whose speed V₁ is lower than the speed V₂ of the delivery conveyor 4. In the apparatus according to the fifth embodiment shown in Fig. 8, the number 10 designates the group of many rollers revolving along a predetermined orbit while rotating. The path of orbital motion is rectilinear in its lower part. The roller group 10 stretches the mass of dough 1 in the range covering the downstream end of the dough-supplying conveyor 3 and the upstream end of the delivery conveyor 4. Thus, a stretching effect similar to that already described is exhibited so as to attain the object of the present invention. As was the case with the second embodiment, the dough is effectively compressed and shaped in the fourth and the fifth embodiments, since the dough-supplying conveyor 3 is inclined upwardly toward the delivery conveyor 4. It will be understood from the foregoing description of the present invention that a mass of dough supplied in an indefinite shape can be stretched into a sheet of dough having a constant volume by making uniform the height of the mass of dough on a dough-supplying conveyor, by detecting a change in the dough width resulting from making the height of the dough uniform, by computing a corresponding speed difference between the dough-supplying conveyor and a delivery conveyor disposed on the downstream side of the supply conveyor and driven at a constant speed, and by driving the dough-supplying roller at the speed corresponding to the computed speed difference. Thus, the present invention solves the prior art defects and can produce a sheet of dough having a high quality, and can do so with a high accuracy.

Claims: A method for continuously compressing a supplied mass of a non-uniform volume per unit length of dough (1) into a dough sheet (2) of a uniform volume per unit length, comprising the steps of: conveying the supplied mass of the non-uniform volume of dough on a supplying conveyor (3) to a delivery conveyor (4) located downstream of the supplying conveyor, compressing the mass of dough on the supplying conveyor into a dough sheet having a uniform thickness, and stretching the dough on the delivery conveyor, characterised by detecting the dough width at the point where the dough is compressed, and setting the speed of the supplying conveyor relative to the speed of the delivery conveyor, based on the detected value of the dough width. The method according to claim 1 further comprising the step of keeping the speed of the delivery conveyor (4) always constant while changing the speed of the supply conveyor (3), so that a continuous dough sheet (2) having a uniform volume per unit length is produced at a constant speed. A dough-stretching apparatus comprising: a dough-supplying conveyor (3) for conveying a continuous sheet of dough and a delivery conveyor (4) positioned in series with and downstream of the supplying conveyor, a compressing means (5;7;8;10) for applying pressure to the dough, disposed at the downstream end of the supplying conveyor, characterised by a dough-width measuring device (11) located near the compressing means, connected to a means (12) for controlling the relative speed of the supplying conveyor and the delivery conveyor, and the dough-width measuring device and control means being adapted so as to measure the width of the dough when it is compressed by the compressing means and to change the speed of the supplying conveyor relative to the delivery conveyor in relation to the measured dough width before it is supplied onto the delivery conveyor, so as to produce a dough sheet of a uniform width and thickness. The dough-stretching apparatus of claim 3 in which the delivery conveyor (3) operates at a constant speed and the speed of the supplying conveyor (4) is controllable by the control means (12) in inverse proportion to the measured value of the dough width. The dough-stretching apparatus of claim 3 or 4, further comprising a second compressing means (6;9), disposed above the delivery conveyor, to adjust the thickness of the dough sheet to be produced. The dough-stretching apparatus of any of claims 3 to 5 in which the first compressing means (5;8) and, if present, the second compressing means (6;9) comprises or comprise a pressure applying roller. A dough-stretching apparatus as claimed in any of claims 3 to 6, wherein the compressing means comprises one or a plurality of rollers (7;8;9;10) located above and adjacent the area between the downstream end of the supplying conveyor (3) and the upstream end of the delivery conveyor (4), the roller or rollers reciprocating over a predetermined range while rolling along the moving path of the two conveyors. A dough-stretching apparatus as claimed in any of claims 3 or 4, wherein the compressing means comprises a plurality of freely rotatable rollers (10) spaced apart from each other and from the conveyors and above the area between the downstream end of the supplying conveyor (3) and the upstream end of the delivery conveyor (4), the rollers orbiting above said area, the dough being supplied into the space between the rollers and the upper surface of the supplying conveyor and causing the rollers to rotate by friction with the dough sheet.

Inventors: HAYASHI TORAHIKO, MORIKAWA MICHIO, HAYASHI, TORAHIKO, MORIKAWA, MICHIO
Applicants: RHEON AUTOMATIC MACHINERY CO, RHEON AUTOMATIC MACHINERY CO. LTD.
Application year: 1990
Main classification: A21C3
IPC codes: A21C3, A21C11, A21D8