WO1997026792A1

WO1997026792A1 - Handling materials

Info

Publication number: WO1997026792A1
Application number: PCT/GB1997/000190
Authority: WO
Inventors: Mark Williamson; Leslie Theophilus Baines
Original assignee: Mark Williamson; Leslie Theophilus Baines
Priority date: 1996-01-25
Filing date: 1997-01-22
Publication date: 1997-07-31
Also published as: AU1450897A; GB9601516D0

Abstract

A sticky dough sheet can be rolled out between a lower series of rollers (5) and an upper support (6), such as a second series of rollers (6), defining a passageway having a reducing gap. Fluid, such as pressurised air is directed upwardly onto the dough sheet between the lower rollers through perforated plates (7) to give a layer of pressurised air. Fluid may also be directed downwardly onto the dough sheet through jets (9). The upper support (6) and the lower rollers (5) can be moved apart for cleaning.

Description

HANDLING MATERIALS

TECHNICAL HELP

This invention relates to the handling of plastic or malleable materials

and is particularly concerned with the rolling of dough to form dough sheets

for use in the manufacture of dough products such as biscuits, crackers,

pizza bases and the like.

BACKGROUND ART

In the automated production of rolled dough sheets, one conventional

process involves passing dough through successive roller nips having

progressively decreasing gap sizes so that the thickness of the dough is

progressively reduced, typically from say 25mm to 0.5mm.

Each roller nip gives rise to a thickness reduction in the range of say

2:1 to 5:1. It is very important to ensure gradual, carefully controlled rolling

of the dough. This is because the dough constitutes a complex polymeric

material, and the properties of the eventual dough product depend on the

molecular and physical structure imparted to the dough sheet by the rolling

process.

In particular, as the dough passes through a roller nip, various factors

affect the compression and linear extrusion of the dough which occurs at

the nip. Thus, by way of example, there is a tendency for dough to 'skid'

on the rollers and 'bunch' at the entrance to the nip; the dough 'relaxes'

and expands on leaving the nip; dough leaving the nip is sticky and wraps round the rollers and has to be peeled off by scrapers; 'skidding' can occur

at the peel off position.

These factors have to be carefully controlled. If this is not done there

may be an undue expansion or stretching or other structural distortion or

stress which, for example, may result in a manufactured biscuit being

undesirably hard rather than soft and flaky.

With the aim of achieving control it is usual practice to adjust roller

speeds as between successive nips and also as between the two rollers in

each nip. It is also known to use conveyors running at carefully matched

speeds receiving dough from the nips. Roller and conveyor speeds may be

pre-set and/or may be varied in response to outputs from optical sensors

monitoring the profile of the dough before or after the nip.

As an alternative to fixed roller nips it is known to use a series of

rollers around the periphery of a large drum or elongate conveyor running

above a transport path defined by a series of horizontal conveyor runs. A

tapered gap is defined between the rollers and the transport path. With

this arrangement considerable thickness reduction can be achieved without

requiring successive separate nips. However, there is still a problem of

matching the speed of the conveyor transporting the dough sheet with the

acceleration caused by the thinning of the sheet. Several successive short

lengths of conveyor running at faster and faster speeds may be used as a

compromise, but this obviously does not match the continuous thinning of the dough sheet. It also leads to complex and numerous drive systems for

the conveyors. The dough sheet is still 'sheared' rather than 'stretched'

because the top surface is not moving at the same speed as the bottom

surface.

DISCLOSURE QF THE INVENTION

An object of the present invention is to provide handling apparatus

with which the thickness of a malleable, sticky material, such as dough,

can be efficiently reduced in an adequately controlled manner.

According to one aspect of the present invention there is provided

handling apparatus for reducing the thickness of a sheet of plastic or

malleable material, said apparatus comprising a series of side by side

rotatable rollers facing and spaced from a support and defining therewith

a passage of reducing gap from an input end to an output end to receive

therethrough the said sheet of material, and wherein fluid flow means is

provided for directing fluid onto the sheet of material within the passage

between the said rollers.

With this arrangement, carefully controlled thickness reduction can

be achieved along the length of the passage with the fluid flow acting to

give smooth transfer of the sheet material from roller to roller, even in the

case of a sticky material such as dough. Undue stress in the material can

therefore be avoided, and thickness reduction can be effected in a

particularly convenient and efficient manner. It can be arranged that the dough sheet moves at exactly the speed it requires for minimum stress.

In a particularly preferred embodiment, the rollers and support are

arranged so that the passage is inclined downwardly from the input to

output ends so that gravity assists movement of the material.

Most preferably the rollers are disposed beneath the said support.

With regard to the fluid flow between the rollers this is preferably

such as to define a fluid bearing or fiuidized bed and therefore may comprise

multiple small outlets in a surface, particularly a planar surface to produce

a thin layer of fluid between such surface and the said material on which

the material can 'float'. This surface is preferably offset beneath the

uppermost peripheries of the adjacent rollers. Preferably all such surfaces

are aligned with each other.

The fluid is preferably air.

The axes of the rollers are preferably parallel to each other and

contained in a common plane.

Slightly different diameters of rollers may be chosen to ensure no

'build-up' occurs in front of any particular roll (i.e. running the last 3 rolls

of a set slightly underfed.

With regard to the support this may be of any suitable structure but

preferably also consists of a series of rollers with fluid directed onto the

sheet of material therebetween derived from the aforesaid fluid flow means

(or from a separate fluid flow means). Especially in the case where the support is above the first said series of rollers, the fluid flow is preferably

such as to deflect the material away from the support for release purposes

and also to provide some drying effect useful where the material is of a

sticky nature such as dough. Thus the fluid flow may be directed from jets

e.g. air jets in surfaces between rollers of the support.

Conventional stripping knives on the rollers are not necessarily required.

The rollers of the first said series are preferably respectively aligned

with the rollers of the support to define nips therewith. The axes of the

rollers of the support are also preferably parallel to each other and contained

in a common plane.

The gap between the rollers of the first said series and the support

is preferably tapered from the inlet to outlet ends. Preferably also the gap

is adjustable e.g. by bodily movement or pivoting of the support and/or the

first said series of rollers to adjust the mutual spacing therebetween and/or

the relative inclination thereof.

Provision may be made for separating the first said series of rollers

and the support for access for cleaning purposes e.g. by pivoting the

support away from the series of rollers. Also, there may be separable

cheeks or flange plates at the ends of the rollers, also to facilitate cleaning.

With conventional nip rollers used with dough sheets, the rollers have end

flanges to prevent sideways displacement of the dough and this makes cleaning difficult. The above described arrangement of separable cheeks or

flange plates gives greater convenience for cleaning.

The apparatus of the invention may comprise two or more sets of

said first rollers with their respective supports so that the thickness of the

material can be reduced in two or more successive steps. The apparatus

may also include conventional nip rollers if desired e.g. for a final thickness

reduction of the material.

It is visualised that the invention will find particular application in the

context of the thickness reduction of dough sheets.

Thus, and in accordance with a further aspect of the present

invention there is provided a method of reducing the thickness of a dough

sheet characterised by the use of apparatus as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described further by way of example only

and with reference to the accompanying drawings in which:-

Fig. 1 is a diagrammatic side view of one form of apparatus

according to the invention; and

Fig. 2 is a top view of a detail of the apparatus of Fig. 1 to a

larger scale.

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in the drawings, apparatus for use in reducing the

thickness of a dough sheet has a downwardly inclined transport path defined between two thickness reduction devices 1 , 2 and a final nip

defined between two rollers 3, 4.

Each of the two devices 1 , 2 comprises two sets of rollers 5, 6. The

rollers 5, 6 of each set have mutually parallel axes contained in a common

downwardly inclined plane. One set of rollers 5 is disposed below and

spaced from the other set with the rollers 5 in the lower set respectively

aligned with those of the upper set to define successive nips therebetween.

As shown in the drawing there are four rollers 5, 6 in each set and

the gaps at the nips are successively reduced effectively to define a tapered passage from an upper inlet end to a lower outlet end of the device 1 , 2.

The inlet end of the lower device 2 is of smaller gap size than the outlet end

of the upper device 1 , and the gap size of the nip between the rollers 3, 4

is smaller than that of the outlet end of the lower device 2.

Between the bottom rollers 5 of each device 1 , 2 there are perforated

air plates 7. These run longitudinally and have upper flat surfaces 8 which

lie in a common plane parallel to the plane containing the axes of the rollers

5 and below the top peripheries of the rollers 5. Air distributor pipes are set

into the plates 7 and communicate with the plate perforations which open

at the upper flat surfaces 8 of the plates 7. The pipes are connected to a

source of pressurised air which escapes through the perforations to produce

a layer of pressurised air over the surfaces 8, in the manner of an air

bearing. The air may be highly compressed or at a lower positive pressure. Between the upper rollers 6 of each device 1 , 2 there are also

perforated air plates 9 similar to the plates 7 between the lower rollers 5

and connected to the same source of compressed air. The perforations may

be the same as those in the lower plates 7, or may be coarser to give wider

jets of downwardly directed air.

At opposite end regions of the rollers 5, 6 there are respective side

cheeks 10 (Fig. 2) which close the sides of the passage defined between

the rollers 5, 6. These can be pulled away to provide easy access to the

rollers 5, 6 for cleaning purposes. The air plates 7, 9 can also be removed

for cleaning.

The bottom set of rollers 5 of each device 1 , 2 is mounted in a fixed

position on a fixed framework 11. The upper set of rollers 6 is adjustably

mounted on upstanding extension plates 12 forming part of the

framework 1 1. The rollers 6 of the upper set are mounted between frame

elements 13 which are engageable at their forward and rearward ends with

mounting axles 14, 15. These axles 14, 15 are positionally adjustable by

means of an eccentric drive to adjust the separation with the lower set of

rollers 5. By adjusting both ends it is possible to adjust both the overall

spacing and also the inclination of the top set relative to the lower set of

rollers 5, 6.

It is also possible to detach the front end of the upper set of rollers

6 so that this set can be pivoted upwardly to facilitate cleaning as shown in broken lines 16 in Fig. 1.

The apparatus so far described is used to reduce the thickness of a

dough sheet which is fed through the passage of the upper device 1 , then

through the passage of the lower device 2 then through the final nip rollers 3, 4.

The air bed between the lower rollers 5 of each device 1 , 2 ensures

easy separation of the dough from the lower rollers 5 so that the dough

moves smoothly from roller 5 to the next roller 5 without undue stress or

bunching or sticking or skidding. The air jets between the top rollers 6

prevent or minimise sticking of the dough to the top rollers 6 by a drying

action and also by a deflection action. The air bed between the lower

rollers 5 also provides a drying action which is helpful for sticky dough.

The downward inclination of the passages also facilitates smooth

stress-free dough movement due to the action of gravity.

The adjustment of the spacing and inclination of the rollers 5, 6 can

be pre-set or may be adjusted in use e.g. in accordance with feed-back

signals from an optical sensor or the like.

The rollers 5, 6 are driven as shown from a motor using drive belts

17 and gears.

With the arrangement described it is possible to achieve thickness

reduction without undue undesirable stress or distortion in a particularly

efficient manner and with convenient easy to clean apparatus. It is of course to be understood that the invention is not intended to

be restricted to the details of the above embodiment which are described

by way of example only.

Claims

1. Handling apparatus for reducing the thickness of a sheet of plastic or

malleable material, said apparatus comprising a series of side by side

rotatable rollers (5) facing and spaced from a support (6) and defining

therewith a passage of reducing gap from an input end to aπ output end to

receive therethrough the said sheet of material, and wherein fluid flow

means (7, 8) is provided for directing fluid onto the sheet of material within

the passage between the said rollers (5).

2. Apparatus according to claim 1 characterised in that the passage is

inclined downwardly from the input to output ends.

3. Apparatus according to claim 1 or 2 characterised in that the rollers

(5) are disposed beneath the said support (6).

4. Apparatus according to any one of claims 1 to 3 characterised in that

the fluid flow means comprises multiple small outlets in a surface (8)

between adjacent rollers (5).

5. Apparatus according to ciaim 4 characterised in that the said surface

(8) is planar.

6. Apparatus according to claim 4 or 5 characterised in that the said

surface (8) is offset beneath the uppermost peripheries of the adjacent rollers (5).

7. Apparatus according to any one of claims 4 to 6 characterised in that

there is a respective said surface (8) between each pair of adjacent rollers (5) and all such surfaces are aligned with each other.

8. Apparatus according to any one of claims 1 to 7 characterised in that the fluid is air.

9. Apparatus according to any one of claims 1 to 8 characterised in that

the axes of the rollers (5) are parallel to each other and contained in a common plane.

10. Apparatus according to any one of claims 1 to 9 characterised in that

the rollers (5) have different diameters.

11. Apparatus according to any one of claims 1 to 10 characterised in

that the support consists of a series of rollers (6) with fluid arranged to be

directed onto the sheet of material therebetween.

12. Apparatus according to claim 11 characterised in that the fluid is

arranged to be directed from air jets (9) between the rollers (6) of the

support.

13. Apparatus according to claim 11 or 12 characterised in that the

rollers (5) of the first said series are respectively aligned with the rollers (6)

of the support to define nips therebetween.

14. Apparatus according to claim 13 characterised in that the axes of the

rollers (6) of the support are parallel to each other and contained in a

common plane.

15. Apparatus according to any one of claims 1 to 14 characterised in

that the gap between the rollers (5) of the first said series and the support - 13 -

(6) is tapered from the inlet to outlet ends.

16. Apparatus according to claim 15 characterised in that the gap is

adjustable.

17. Apparatus according to any one of claims 1 to 16 characterised in

that the first said series of rollers (5) and the support (6) are separable.

18. Apparatus according to claim 17 characterised in that the rollers (5)

have separable cheeks (10) at the ends thereof.

19. Apparatus according to any one of claims 1 to 18 characterised in

that there are two or more sets of said first rollers (5) with their respective

said supports (6).

20. A method of reducing the thickness of a dough sheet characterised

by the use of apparatus according to any one of claims 1 to 19.