GB2457269A

GB2457269A - A press for compressing tortilla

Info

Publication number: GB2457269A
Application number: GB0802327A
Authority: GB
Inventors: Robert Frederick Jackson
Original assignee: JBS MASTER BAKER Ltd; JBS PROCESS ENGINERRNG Ltd
Current assignee: JBS MASTER BAKER Ltd; JBS PROCESS ENGINERRNG Ltd
Priority date: 2008-02-07
Filing date: 2008-02-07
Publication date: 2009-08-12
Also published as: GB0802327D0

Abstract

The invention relates to a tortilla press (10) to compress uncooked dough into the required shape for a tortilla. The press (10) includes a platen (14) having a downwardly facing planar surface, heating elements to heat the surface and a planar support surface (13) (comprising a conveyor belt 11) on which dough portions are deposited. The platen (14) is mounted to be moveable between a raised position allowing the dough portions to lie between the platen (14) and the support surface (13), and a lowered position in which the beatable surface is adjacent the support surface (13), for the dough portions to be compressed. A plurality of raising means (hydraulic cylinders 19), act in synchronous fashion to move the platen (14) between the raised and lowered position to ensure that the downwardly directed surface of the platen 14 remains horizontal. The distance between this surface and the belt 11 should remain constant.. The distance by which each cylinder 19 moves the platen 14 can be individually set. The motions of belt 11 and the horizontal motion of the platen 14 are synchronised to ensure that they move at the same speed. To improve the conformation of the downwardly facing planar surface a plurality of continuously adjustable pressure elements (62) are provided.

Description

* 1 2457269

AN IMPROVED TORTILLA PRESS

Field of the Invention

The field of the present invention is that of an apparatus for pressing and working dough. The apparatus is particularly intended for use in the production of tortillas.

Background to the Invention

The production volume of tortillas, with which the present invention is particularly, although not exclusively concerned, has increased substantially in recent years due to changes in eating patterns. In order to keep pace with requirements the process of manufacture has been automated wherever possible. Moreover, continuous processes have also been introduced to increase production numbers.

The present invention is concerned with one particular stage of the process: the conversion of an amorphous lump of uncooked dough into the well-known, flat tortilla shape which is ready for further processing including cooking, packaging and despatch.

A number of methods are known in the art to carry out this stage. Some of these are based around the use of a heated platen press of sufficient size to produce a plurality of tortillas simultaneously. In such presses, dough balls are placed onto a flat surface, beneath the heated platen. The platen is then lowered to within a few millimetres of * the surface. The platen is maintained in this position for a preset time period. This action squashes the dough balls into the flat tortilla shape, which process is facilitated * S. ** 2:: **S by the heating, which alters the flow characteristics of the dough. The dough is then removed for further processing and another batch of dough balls put on the surface, enabling the process to be repeated.

In practise, the process is part-automated in that the surface comprises part of a conveyor belt which transport the dough balls beneath the platen. The platen in the prior art is then constrained to move solely in the vertical plane.

A variation on this procedure is introduced in US 4 938 126 which discloses the use of a reciprocating platen travelling with the moving conveyor belt whilst the forming process is carried out, the platen then returning back to a starting position in order to form a further batch.

The above methods and apparatus require a high level of precision to within a millimetre or so in order to maintain the platen at the same distance from the conveyor surface across the whole width and length of the platen. If this distance is not accurately maintained then the tortillas ultimately produced will be of inferior quality and will normally have to be thrown away, thereby wasting materials and energy. It is not unusual, using existing presses; for wastage rates in excess of 25% to be reached.

The means of adjusting the distance is such that correction of any error requires the apparatus to be taken off line for several hours at a time. Moreover, because making a suitable correction is not always a simple action to take, even for an experienced operator, and can only be checked by reassembling the apparatus and starting a new run, this downtime can be increased considerably.

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* . .*5 5 5 3 * *:.** :: * S * *SS * * S.. ..* A typical platen has 20 to 30 adjustment points in which shims, often of the order of 0.5mm or less in thickness can be inserted to alter the profile of the platen surface.

The shims act to exert pressure on the lower surface of the platen, pushing it downwards, and decrease the gap, over a small region, between the platen and the conveyor surface.

It is therefore advantageous to provide an apparatus in which downtime is reduced and the present invention seeks to provide such an apparatus. In so doing the production costs and raw material costs are improved.

Summary of the Invention

According to the invention there is provided a tortilla press, the press comprising a platen having a downwardly facing planar surface, heating elements to heat said planar surface, a planar support surface on which dough portions are deposited, the platen being mounted for movement between a raised position allowing the dough portions between the platen and support surface; and a lowered position in close spaced relationship to the planar surface, whereby dough portions are compressed, wherein the platen is operably mounted to a plurality of raising means synchronised to move the platen between the raised position and the lowered position. The provision of a plurality of raising means facilitates flexibility and spreads the load being borne by the raising means.

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S * S * *.. *.S Preferably each raising means is individually adjustable to adjust the distance between the raised position and the lowered position. The relative orientation of the planar surface of the platen and the support surface can be easily altered to improve the product quality. Especially, preferably each raising means is a hydraulic cylinder which provides the necessary strength and fine adjustment. Alternatively, each raising means comprises a servo driven ball screw, which facilitates installation and maintenance.

Particularly conveniently the platen is operatively mounted to four cylinders, one cylinder at each corner of the platen. A fine control in the adjustment of the height of the platen is thereby achievable. Further, particularly conveniently, the cylinders are mounted to the side of the planar surface so that in the event of, for example, leakage from a cylinder, the platen is not contaminated and there is no risk of cylinder fluid falling onto a heating element.

Optionally, the press further comprises a plurality of continuously adjustable pressure elements to exert pressure on the upper surface of the platen, thereby altering the conformation of the downwardly facing surface of the lower surface.

The pressure elements facilitate fine adjustments required to bring the downwardly facing platen surface into correct, normally parallel alignment with the planar support surface.

S **S * S *** 1: S.' Optionally, the planar support comprises a continuous belt moveable horizontally with the platen. An automated batch process is thereby facilitated which speeds up production of product.

Preferably, the platen moves horizontally in synchronised motion with the planar support surface in the lower position for sufficient time to form a dough portion. A further increase in throughput of product is thereby achieved.

Brief Description of the Drawin2s

The invention is described with reference to the accompanying drawings which show by way of example only, one embodiment of a tortilla press. In the drawings: Figure 1 is a perspective view of a press; Figure 2 is a side view of a press; Figure 3 is an end view of a press: Figure 4 is a top view of a press: Figure 5 illustrates layouts of dough portions on the press: and Figure 6 illustrates a shimming bolt.

Detailed Description of the Invention

The invention as herewith disclosed is designed to improve the efficiency of a tortilla production process in which uncooked portions of dough are formed into the recognisable flat tortilla shape. The apparatus described has a flat support surface on S * .** S S *S 6 *: *.. 555 which an amount of uncooked dough, often predominantly spherical in shape, is deposited. A platen, including one or more heating elements is brought down onto the dough until the heated platen surface and the support surface are almost touching.

The dough is thereby forced into a flat disc shape, a process aided by the high temperature of the platen which alters the flow characteristics of the dough.

The apparatus shown in the drawings has a reciprocating platen and a conveying surface to support the dough. The platen and the conveyor are set to move laterally at the same velocity which preserves the relative positions of the platen and the dough.

Referring now to the drawings in Figure 1 a press apparatus, generally referenced 10, is intended to be part of a manufacturing chain in which the press 10 receives prepared, uncooked portions of dough, which the press 10 shapes, the shaped product then being forwarded on to, amongst other stations, a cooking and a packaging station.

As such, the apparatus 10 has an endless conveyor belt 11, driven by a series of rollers 12. The conveyor belt 11 is formed of a heat resistant material to enable it to withstand the heating temperature. The belt 11 is supported along the upper portion to ensure it does not sag, but remains flat. Moreover, the upper surface 13 directly supporting the dough is smooth to reduce loss and facilitate removal of the tortilla and cleaning the belt 11. The smoothness also ensures that the distance between the belt 11 and a platen 14 (see below) remains constant. A cleaning and drying station can be included if desired to ensure that the belt remains in a good condition.

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The platen 14 is rectangular or square in shape having, in the exemplified press 10, a width and length both of 1300mm. The actual size of the platen 14 will however depend upon the use for which the press 10 is designed. A supporting framework 15 holds the platen 14 in position, facilitates adjustment of the platen 14, and connects the platen 14 to the movement mechanisms.

In order to correctly function, the platen 14 needs to be able to move both horizontally and vertically. The horizontal motion is driven by means of a ball screw (not illustrated) although other means known in the art can be used. The motions of the conveyor belt 11 and the horizontal motion of the platen 14 are synchronised by servo units, ensuring that the two elements 11, 14 move together at the same velocity when required.

The framework 15 has a lower carnage 16 directly connected to the drive mechanism.

Four support pillars 17 extend upwardly from the lower carriage 16 to support an upper carriage 18. Also connected to both the lower carriage 16 and the upper carriage 18 are four hydraulic cylinders 19 which are operable to change the distance between the upper and lower carriages (18, 16).

Vertical motion of the platen 14 is driven by the four hydraulic cylinders 19, whose movement is co-ordinated to ensure that the downwardly directed surface of the platen 14 remains horizontal. As indicated earlier, it is important that the distance between this surface of the platen 14 and the conveyor belt 11 remains constant across the whole length and width of the surfaces.

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The cylinders 19 drive the platen 14 between an upper raised position and a lower position. The distance by which each cylinder 19 moves the platen 14 can be individually set. It will be appreciated therefore that having each cylinder 19 individually adjustable, allows careful control of the relative position of the downwardly facing surface of the platen 14 and the upper surface of the belt 11.

Where a problem with the shape of the product produced is observed therefore, simple adjustment of one or more of the cylinders 19 can rectify the problem. Such rectification can be carried out either when the press 10 is at a standstill or whilst it is running. Control can be carried out either directly on a cylinder 19 or can proceed via control panel 22. Obviously, where the adjustment can be made whilst the above described forming process takes place, this is to be preferred as production loss is minimised.

The use of cylinders 18 to the side of the conveyor belt 11 has been found to be advantageous compared with an alternative of using hydraulic rams above the platen 14. Although the use of a single overhead ram is known, the vertical height of the press 10 is then greater due to the ram and the supporting structure required.

Moreover, in the event of any leakage of fluid from the ram or rams, the platen and the conveyor are likely to be contaminated.

In use therefore, the conveyor belt 11 is set in motion by the rollers 12. Portions of uncooked dough are delivered onto the conveyor 11 at predetermined positions. Once the preset number of portions have been delivered, the heated platen 14 is lowered to within around 1.0-1.5mm of the conveyor belt's surface. The dough portions are

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thereby compressed into a disc shape. Examples of layouts of dough on the conveyor belt 11 are shown in Figures 5.

Once the platen 14 is in the lowered position the horizontal motion of the platen 14 and the conveyor belt 11 is synchronised so that the dough remains in contact with the heated platen 14 for a preset length of time, typically around 1.55. In that time, the dough is sufficiently formed to be ready for further processing.

Once the processing time is reached, the platen 14 is raised and brought back to its initial position ready to be used on a further set of dough portions. The formed product meanwhile is carried by the conveyor belt 11 to the end of the press 10.

The formed product or samples thereof will normally be subject to an inspection regime to ensure that quality is maintained. If it becomes apparent from said inspection that the heating and forming process is not being carried out properly, then action will need to be taken. Normally deficiencies are caused by the distance between the platen 14 and the conveyor belt 11 being incorrect. Additionally, it is usually found that the incorrect distance applies only to one portion of the platen 14 and that the rest of the platen 14 is in good alignment.

It is at this stage that the prior art machines would need to be stopped and adjusted for an extended period. Typically the adjustment needing to be made is of the order of a millimetre or less. Nevertheless such a small amount can have a significant impact on product quality. In accordance with the invention however, the platen is adjusted more rapidly.

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* * *S * * S S S. ** . . . . S 10: : .:. ::: * * * :.. * * S.. *S* One means of adjusting the orientation of the platen 14 is to adjust the distance between the raised position and the lowered position for an individual cylinder 19 as described above, and this is the primary means of adjustment contemplated.

In addition, and turning to Figure 4, the platen 14 can be seen to be spacedly mounted to a flat plate 20 itself mounted to the upper carriage 18. Within the space, between the platen 14 and the plate 20 are housed heating elements to raise the surface of the platen 14 to the required temperature. The flat plate 20 includes a number of throughapertures. Located through each of these apertures is a shimming bolt 21 which can engage the rear surface of the platen 14. By adjusting the extent to which each individual bolt 21 presses against the platen 14 therefore, the configuration of the heated platen 14 coming into contact with the dough can be adjusted by a controllably fine amount. The lack of requirement for shims to be placed between the flat plate 20 and the platen 14 speeds up the process considerably in comparison to the prior art machines.

An embodiment of a shimming bolt 21 is shown in Figure 6. The bolt 21 passes through an aperture 60 in the plate 20, referenced in Figure 4 and acts to exert pressure on the platen 14, the pressure exerted being borne by the plate 20. By adjusting the pressure on the platen 14, the platen's configuration is adjusted to the appropriate one to form the dough.

The bolt 21 comprises a clamp bolt 61 which passes through and holds firmly in position, a shim bolt 62. The shim bolt 62 has a broad, disc-shaped head portion 63 * S ** * * * * ** S. * * . . . ii: : .:.

* * * :.. * * **S *SS connected to a shaft 64, which passes through the aperture 60. A lock nut 65 separates the shim bolt 62 from the upper surface of the plate 20.

In order to move the platen 14 in a downwards direction, the clamp bolt 61 is released. The lock nut 65 is then released allowing the shim bolt 62 to be turned in a clockwise direction. This moves the shim bolt 62 in a downwards direction through the aperture 60 causing pressure to be exerted on the platen 14. To ensure that the bolt 62 does not cause unwanted deformation damage to the platen 14, a resilient member may be located intermediate the lower end of the bolt 62 and the platen 14.

Once the bolt 62 has been moved the desired amount, the clamp bolt 61 is tightened and the lock nut 65 tightened to hold the platen 14 firmly in position.

In order to raise the platen 14, the procedure above is again carried out, with the important difference that the shim bolt 62 is rotated in an anti-clockwise direction, releasing an amount of pressure on the platen 14.

The above operation is carried out with the production halted. On completion of the process, production is restarted and quality controls carried out to ensure that the process is being properly carried out. Normally, when alterations need to be carried out, only one shim bolt 62 is adjusted during any one production halt.

The overall amount of vertical movement permitted to a shim bolt 62 is constrained to be around 2mm or less. It has been found that where the platen 14 is at its highest

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* S * **5 * * S.. *S* point in the region around a particular shim bolt 62, then adjustment of the surrounding points will have to take place.

Although not illustrated, it can be envisaged that the pressured applied by each bolt 21 can be adjusted from a control panel 22 such as is illustrated in Figure 1. In the embodiment shown (see Figure 4) adjustment can be carried out with a conventional spanner.

It is furthermore envisaged to carry out adjustment of the shim bolts through the use of suitably configured servomotors. The servomotors are under the control of an operator inputting the required adjustments by means of the control panel 22. It is also envisaged that adjustment is under the control of a processing unit, the processing unit receiving information on the quality of the formed dough portions in order to determine adjustments necessary.

As illustrated in Figures 1-4, the platen 14 is around 50mm in thickness to provide a long wearing and robust element. However, if so desired a thinner sacrificial plate, perhaps of the order of 5mm in thickness can be overlaid on a thicker backing plate to provide a cheaper, replaceable feature. i3

Claims

Claims 1. A tortilla press 10), the press (10) comprising a platen (14) having a downwardly facing planar surface, heating elements to heat said planar surface, a planar support surface (13) on which dough portions are deposited, the platen (14) being mounted for movement between a raised position aliowing dough portions between the platen (14) and support surface 13); and a lowered position in close spaced relationship to the support surface (13), whereby dough portions are compressed, wherein the platen (14) is operably mounted to a plurality of raising means (19) synchronised to move the platen (14) between the raised position and the lowered position. * S. * S * * S*

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2. A press according to Claim 1, wherein each raising means (19) is individually adjustable to adjust the distance between the raised position S..... * *and the lowered position.
3. A press according to Claim 2, wherein each raising means is a hydraulic *S.S.SS Scylinder.
4. A press according to Claim 2, wherein each raising means comprises a servo driven ball screw.
5. A press according to any preceding Claim, wherein the platen is operatively mounted to four cylinders, one cylinder at each corner of the platen.
6. A press according to Claim 5, wherein the cylinders are mounted to the side of the planar surface.
7. A press according to any preceding Claim, wherein the press further comprises a plurality of continuously adjustable pressure elements (62) to exert pressure on the upper surface of the platen, thereby altering the conformation of the downwardly facing planar surface.*:*::*
8. A press according to any preceding Claim, wherein the planar support s.'. surface comprises a continuous belt (11) moveable horizontally with the S...platen.S..... * 0

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9. A press according to any preceding Claim, wherein the platen moves *SS.horizontally in synchronised motion with the planar support surface in the 0****S -c/ lower position for sufficient time to form a dough portion.
10. A press substantially as herein described with reference to and as illustrated in the accompanying drawings. * I. * * * * ** S... * SS..... * S * a S...* * 15SS SS*..I.. a