GB2031328A - Improvements in the production of biscuit dough - Google Patents

Abstract

Dough from a bulk supply conveyor 11 and hopper 10 is sheeted directly to a thickness suitable for baking biscuits by passage of the dough through a three roll unit 12, 13, 14 which provides between the rolls successive gaps, the first 15 of which does not exceed 10 mm in width and the second 16 of which does not exceed 5 mm in width, the ratio of the widths of the two gaps 15, 16 being approximately 2:1. The supply level is controlled by a capacitance probe 17 and the thickness of the dough sheet is controlled by a sensor 19. The shafts 27, 31 of rolls 13, 12 are mounted eccentrically to enable gap adjustment. Roll 13 is provided with longitudinally extending flutes (21, Fig. 2 not shown) to direct the dough into gap 15 and rolls 12, 14 are provided with an anti-friction coating e.g. sprayed molybdenum and p.t.f.e. <IMAGE>

Description

SPECIFICATION Improvements in the production of biscuit dough In the production of biscuits, dough is mixed in bulk quantities and then formed into a continuous sheet of a given thickness from which biscuit shapes are formed for baking. Basically there are three types of biscuit, sweet, semi-sweet and crackers. In the case of sweet and certain semisweet biscuits, the sheet of dough is fed to the biscuit forming apparatus, while in the case of crackers and other kinds of semi-sweet biscuits the sheet is fed to dough lapping equipment for laminating before forming.

The thickness of the sheet required for forming or laminating is usually 1 to 3 mm and, to achieve this, the bulk dough is fed to sheeting apparatus, followed by one or more gauge roll units. The sheeter normally consists of a dough hopper mounted above an assembly of rolls which produces a sheet having a thickness of 8 to 1 5 mm. A gauge roll unit consists of a pair of rollers through which the sheet is passed, the gap between the rolls being set to reduce the sheet thickness. Frequently two or more gauge roll units are provided so that the sheet is gradually reduced to the final required thickness of 1 to 3 mm.

A typical known sheeter has, in the outlet of the hopper, a pair of horizontal rolls disposed at the same level and providing between them a relatively wide outlet gap for the dough and a third lower roll which cooperates with one of said rolls to form a sheeting gap, the width of which can be adjusted within the range of 8 to 1 5 mm, no adjustment of the outlet gap being necessary when adjustment of the sheeting gap is made.

It has been the invariable practice in the industry to provide for reduction of the thickness of the sheet of dough after sheeting by at least one gauge roll unit because it was thought that too drastic a transformation of bulk dough into a thin sheet of thickness 1-3 mm would be detrimental to the dough and, indeed, impossible to achieve. The necessity for providing at least one gauge roll unit not only increases substantially cost of a biscuit making plant but increases substantially the space required to accommodate the equipment involved.

The present invention is based on the appreciation of the fact that it is possible to sheet the dough directly to a gauge thickness of the order of 1 to 3 mm, and so dispense with the necessity of a gauge roll unit between the sheeter and the forming apparatus or lapping equipment, provided the sheeter is correctly designed.

In the first place, in addition to providing a sufficiently narrow gauging gap between the lower roll and the cooperating roll, we have found that the gap between the two upper rolls, herein termed the forcing gap, must be considerably narrower than heretofore, and must be reduced to a width of approximately twice that of the gauging gap. Secondly, it is necessary, when adjusting the gauging gap to produce gauged sheets of different thickness, also to adjust the forcing gap to maintain a ratio of approximately 2:1 between the widths of the two gaps.Thirdly we have found when it is sought to modify a conventional sheeter in this way, such high pressures are created between the rolls providing the gauging gap that it is highly desirable to provide these rolls with a thin surface coating of anti-friction material, e.g. a metal matrix impregnated with a friction reducing plastics material, for example polytetrafluoroethylene.

The invention accordingly provides a method of producing a sheet from a bulk supply of biscuit dough, which comprises feeding the dough continuously between two positively driven rolls providing between them an adjustable forcing gap not exceeding 10 mm in width and then between one of these rolls and another positively driven roll providing an adjustable gauging gap not exceeding 5 mm in width, the width of the forcing gap being approximately twice that of the gauging gap.

One embodiment of apparatus for carrying out the method according to the invention is illustrated, by way of example, in the accompanying drawings, in which: Fig. 1 is a diagram showing the basic elements of the invention, Fig. 2 is a view on a larger scale of parts of the rolls forming the forcing gap, Fig. 3 is a front elevation, partly in section, showing the drive to the rolls and mechanism for adjusting the two gaps, and Fig. 4 is a vertical section, with the flutes on the forcing roller omitted.

As shown in Fig. 1 , the apparatus includes a hopper 10, to which bulk dough to be sheeted is supplied by a belt conveyor 11. Beneath the hopper 10 are three rolls 12, 13, 14 which respectively have diameters of 420, 300 and 230 mm and which are rotated about horizontal axes in the directions shown by the arrows by mechanism described below.

The rolls 12 and 13 cooperate to provide a forcing gap 1 5 for passage of dough from the hopper 10 to a gauging gap 16 between the rolls 12 and 1 4. The forcing gap 1 5 is adjustable to a value in the range of 5-10 mm, and the gauging gap 16 is adjustable to a value in the range of 1 to 5 mm, the adjustments made being such that the ratio of the width of the forcing gap to that of the gauging gap is approximately two to one. These adjustments are made as described below, either manually or by means of servo motors.

With the apparatus working within this range of gap sizes, it has been found that there are two factors which can result in slight variation of thickness of the dough sheet emerging from the gauging gap 1 6. These two factors are the head of dough within the hopper 10 and variation in the dough recipe. To overcome the first of these a capacitance probe 1 7 is provided within the hopper 10 which senses the level of the dough in the hopper and maintains the head of dough at a required level by controlling a motor 18 driving the conveyor 11 to the hopper. The second is overcome by a sensor 1 9 which measures the thickness of the dough sheet emerging from the gauging gap 1 6 and travelling along a datum plate 20.The signals derived from the sensor 1 9 may be used to effect adjustment of the roll 12 to vary the gauging gap 16, as described below, to maintain the thickness of the sheet at a predetermined value. Alternatively these signals may be used to maintain the thickness of the sheet at the predetermined value by varying the speed of the drive to the rolls 12, 13 and 1 4.

The rolls 12, 13 and 14 are of metal. The roll 13 has, as shown in Fig. 2, longitudinally extending flutes 21 shaped to direct the dough into the gap 15. The radius R of the flutes is preferably 3 mm and the depth S of the flutes 1.5 mm. The other two rolls 12, 14 have smooth surfaces having an anti-friction coating 22 which allows them to slip relative to the dough when pressures approach the level at which shaft breakage would be likely to take place.

Preferably this coating consists of a sprayed coating of molybdenum metal onto which polytetrafluoroethyle ne has been sintered at 3800C. and has a thickness of 0.025-0.07 mm.

This coating material is supplied as Armourmax by Acheson Treatments Ltd.

As shown in Fig. 3, the rolls 12, 13, 14 are driven by a main drive shaft 23, carrying a gear 24 which meshes with a gear 25 on the shaft 26 of the roll 14. The shaft 27 of the roll 13 is driven by meshing gears 58 from the shaft 26. The shaft 27 isjournalled eccentrically in a circular disc 28 which is rotatable about a centre line 29 for the purpose of gap adjustment as later described. The gear 25 drives a gear 30 on the shaft 31 of the roll 12, which is journalled eccentrically in a circular disc 32 which is rotatable. about a centre line 33.

End flanges 34, one of which is shown in Fig. 4, on the roll 14 prevent loss of dough from the cavity between the rolls.

The eccentric bearing supporting the roll 1 3 is adjustable manually for initial set up of the roll gaps by a handwheel 35 on a shaft 36 and also by a servo motor 37 for gap adjustment during operation. The motor 37 drives, through a chain drive 38, a shaft 39 which drives, through worm gearing 40, a shaft 41 carrying a worm 42 meshing with a worm quadrant 43 on the disc 28.

A worm 44 on the shaft 36 meshes with a worm wheel 45 on the shaft 39 for the purpose of manual adjustment.

The eccentric bearing supporting the roll 1 2 is adjustable in similar fashion, manual adjustment being effected by a handwheel 46 and powered adjustment by a servo motor 47 which acts in response to signals from the sensor 19 which senses the thickness of the sheeted dough. The motor 47 drives a shaft 48 through a chain drive 49. The shaft 48 drives, through worm gearing 50, a shaft 51 carrying a worm 52 which meshes with a worm quadrant 53 on the disc 32. A worm 54 operable by the handwheel 46 meshes with a worm wheel 55 on the shaft 48.

Claims (5)

1. A method of producing a sheet from a bulk supply of biscuit dough, which comprises feeding the dough continuously between two positively driven rolls providing between them an adjustable forcing gap not exceeding 10 mm in width and then between one of these rolls and another positively driven roll providing an adjustable gauging gap not exceeding 5 mm in width, the width of the forcing gap being approximately twice that of the gauging gap.

2. A method according to claim 1, which includes the step of measuring the thickness of the sheet of dough delivered from the gauging gap and adjusting the width of the gauging gap in response to variations in the measured thickness of the sheet to maintain the thickness at a predetermined value.

3. A method according to claim 1, which includes the step of measuring the thickness of the sheet of dough delivered from the gauging gap and adjusting the speed of rotation of the rolls in response to variations in the measured thickness of the sheet to maintain the thickness at a predetermined value.

4. A method according to any one of the preceding claims, in which the dough is supplied to the rolls providing the forcing gap from a hopper disposed above these rolls and which includes the step of measuring the head of dough in the hopper and adjusting the rate of supply of dough to the hopper in response to variations in said head to maintain said head at a predetermined value.

5. A method according to any one of the preceding claims in which the rolls providing the gauging gap have a coating of anti-friction material.