BACKGROUND OF THE INVENTION

The present invention relates to a method and assembly for metering dough by means of a metering device comprising: a hopper for the supply of dough to be metered, a piston that is movable in a first chamber, wherein the first chamber connects to the hopper, a blade member that is also movable in the first chamber and arranged between the piston and the hopper, at least one metering chamber, wherein the metering chamber is adapted for in at least one position connecting to the first chamber, and the metering chamber is movable with respect to the first chamber.

Industrial bakeries have been using metering machines for quite some time now for turning a large quantity of dough into smaller portions. The dough is sucked in by a piston from a dough hopper towards a suction chamber, a blade member closes off the opening between the dough hopper and the suction chamber, and subsequently the dough is pushed from a slide into one or several metering chambers. The dough is then ejected out of the metering chamber(s) by means of metering pistons after which it can be sent to the next processing machine via a conveyor belt.

The quantity of dough processed by the slide per stroke depends on the desired volume {weight) per recipe. The desired volume can be set by bounding the metering pistons during filling the metering chamber(s). When the dough is pushed from the slide into the metering chamber(s) by means of the piston this is done with a force exerting pressure on the dough. This pressure has a negative influence on the dough structure, at least in case of highly sensitive dough types.

Patent specification NL 1 ,029,361 describes an embodiment of a metering device wherein the piston and the blade member are individually controllable, and a control device for it which defines the suction stroke magnitude on the basis of the set volume of the metering chamber(s), and wherein the ejection stroke magnitude is adapted on the basis of the measured pressure of the dough in the suction chamber in order to let the dough be pressurised as little as possible in order to preserve the quality of the dough as much as possible.

It has further been provided that the suction stroke of the piston is defined by the set volume of the metering chamber, wherein the volume of the suction stroke is an integer number of times the set volume of the metering chamber, whether or not increased by a predetermined buffer volume. A drawback thereof is that at least a part of the dough is pressurised several times.

In the production of dough products wherein the properties of the dough are easily affected by pressurising it, one will opt for not sucking in more dough than is sufficient for filling the metering chamber(s) once. A drawback thereof is that in that way sometimes dough portions are achieved that deviate from the desired weight.

It will be clear that a further drawback of the known device is that in case of a change in the recipe of the dough or the size of the desired dough portion, the machine parameters of the metering device have to be readjusted each time, depending on the properties of the dough and the shape and content of the metering chamber.

It is an object of the present invention to considerably accelerate and simplify setting an optimal piston stroke magnitude for a metering machine.

SUMMARY OF THE INVENTION According to a first aspect the invention provides a method for setting a piston stroke magnitude of a metering device of an assembly comprising: a metering device according to the preamble; a weighing device, placed downstream from the metering device, for determining the weight of dough portions coming out of the metering chamber; and a control device coupled to both the metering device and the weighing device, adapted for setting a piston stroke magnitude of the piston, wherein the method is characterised by the following steps: i) setting a series of piston stroke magnitudes for a dough product, ii) carrying out a number of metering strokes per piston stroke magnitude, weighing the dough portions resulting therefrom by the weighing device and determining a standard deviation in weight of those portions, iii) determining the optimal piston stroke magnitude for which the standard deviation in weight of the metered dough portions is minimal, iv) setting the optimal piston stroke of the metering device for the dough product by the control device.

In particular the magnitude of the suction stroke is optimised here, i.e. that part of the piston stroke during which dough is sucked in. This is because the quantity of dough present in the first chamber also determines how much pressure is exerted on the dough during the ejection stroke. However, it is also possible to apply the present invention in determining an optimal ejection stroke magnitude, or in determining the optimal setting from a number of combinations of suction- and ejection stroke magnitudes.

When the piston stroke is too large and therefore sucks in more dough into the suction chamber than can be discharged to the metering chamber(s), the surplus of sucked in dough is pressurised several times prior to actually being discharged to the metering chambers. When the piston stroke is too small the desired weight accuracy of the dough piece is not achieved. Determining the piston stroke magnitude from a limited number of piston stroke magnitudes which leads to the highest accuracy in weight comprises metering a number of dough portions for a number of possible piston stroke magnitudes, after which said portions of dough are weighed on a weighing device. The piston stroke magnitude resulting in dough portions having the smallest standard deviation in weight is then set as the optimal piston stroke magnitude.

In particular in an embodiment, when the standard deviation in weight of dough portions for a number of piston stroke magnitudes is substantially the same, that piston stroke magnitude is chosen for which the quantity of dough in the first chamber is as small as possible, or for which the piston stroke is as small as possible.

The standard deviation in weight need not necessarily be linearly related to the piston stroke magnitude; besides the quantity of sucked in dough, factors such as dough composition and shape and content of the metering chamber(s) may influence the standard deviation, so that per dough composition for all piston stroke magnitudes a number of metering strokes has to be carried out in order to be able to determine the related optimal piston stroke.

Due to the automated method according to the invention, when the dough product to be produced is changed, the optimal piston stroke magnitude from a series of piston stroke magnitudes for a metering machine can be determined quickly and easily.

In an embodiment in step ii), prior to carrying out the number of metering strokes, first one piston stroke is carried out of which the resulting dough portions are ignored in the calculation of the standard deviation. In this way it is ensured that the first chamber is sufficiently filled prior to starting with the optimisation.

Although in one embodiment the series of piston stroke magnitudes in step i) can be ranged from small to large, the series of piston stroke magnitudes in step i) preferably are ranged from large to small. By setting the piston stroke magnitudes at consecutive magnitudes the differences between consecutive settings are minimal which reduces the duration of the setting operation.

In an embodiment in step ii) each time after the number of metering strokes has been carried out the next piston stroke magnitude from the series of piston stroke magnitudes is switched to, or when the last piston stroke magnitude had already been set, step iii) is proceeded with. After the number of metering strokes for a piston stroke magnitude has been carried out, the control device sets the metering device to the next piston stroke magnitude, until all piston stroke magnitudes from the series of piston stroke magnitudes have had their turn.

In an embodiment in step ii) each time that the weighing device has not weighed dough pieces for a predetermined time, the next piston stroke magnitude from the series of piston stroke magnitudes is switched to, or when the last piston stroke magnitude had already been set, step iii} is proceeded with.

Shortly after the metering machine has stopped with metering dough portions the weighing device will no longer weigh dough either. During optimisation the metering machine can for instance temporarily stop metering after the pre set optimisation strokes for a piston stroke magnitude have been completed. The time in between the metering of dough and the dough reaching the weighing device is in this case called the cycle time. When it is clear that more time has passed between the various dough weighings than the cycle time, preferably over 30 times the cycle time, then the metering machine will have completed the optimisation strokes for a piston stroke. For this piston stroke magnitude the standard deviation in weight of the dough portions is then calculated, after which the next piston stroke magnitude can be proceeded with. Even when for other reasons the supply of dough portions has stopped for clearly longer than the cycle time, for instance if the hopper were empty, thanks this method the standard deviation in weight of the dough portions produced up until then with the set piston stroke magnitude, is still calculated. In an embodiment the metering device carries out the number of metering strokes at predetermined points in time, independent of the weighing device. In this way it is possible that between the metering device and the weighing device no communication is necessary during carrying out the metering strokes; not until the metering strokes for the entire range of piston stroke magnitudes have been completed and a piston stroke with the smallest standard deviation in weight of the dough portions is known, should it be known at the control device which pistons stroke that is in order to set it in the metering device. By limiting the mutual communication between the metering device and the control device and between the control device and the weighing device to a minimum, it will become easier to for instance use machines from different manufacturers that use different communication protocols. As the machines can work at least substantially individually for a correct execution of the method, the assembly can be built up in a more modular manner and the machines are easier to replace.

In an embodiment of the method the optimal piston stroke magnitude, optionally together with other machine parameters of the (dough) product, is stored to be re-used later. In industrial bakeries often many different types (dozens to hundreds) of dough products are produced wherein the optimal setting of the metering device may be different for each dough product. By storing said machine parameters together with the name of the dough product it becomes possible to use said machine parameters again at a later moment and to set them, at least partially, automatically.

In an embodiment a previously stored optimal piston stroke magnitude and/or other machine parameters related to a dough product are retrieved and used by the control device for setting the piston stroke of the metering device. In that way optimal piston stroke magnitudes found earlier can be set without carrying out the optimisation again, also for identical metering machines in different bakeries.

According to a further aspect the present invention provides an assembly comprising a metering device, wherein the metering device comprises a hopper for the supply of dough to be metered, a piston that is movable in a first chamber, wherein the first chamber connects to the hopper, a blade member that is also movable in the first chamber and arranged between the piston and the hopper, at least one metering chamber, wherein the metering chamber is adapted for in at least one position connecting to the first chamber, and the metering chamber is movable with respect to the first chamber; a weighing device, placed downstream from the metering device, for determining the weight of dough portions coming out of the metering chamber; and a control device coupled to both the metering device and the weighing device, adapted for setting a piston stroke magnitude from a series of predetermined piston stroke magnitudes, wherein the control device is adapted for setting an optimal piston stroke magnitude of the metering device based on the standard deviation of measurements taken by the weighing device. The properties of said assembly render it particularly suitable for use in carrying out the method described above for setting a piston stroke magnitude.

In an embodiment of the present invention the assembly comprises a metering chamber that is closed off at one side by a metering piston driven by a first motor. In that way it is possible to have the setting of the metering volume run automatically.

In an embodiment the assembly comprises a first sensor for determining at what volume the metering chamber has been bounded by the metering piston and for generating a first feedback signal on the basis thereof. Such a means preferably is a potentiometer, preferably coupled to the first motor. The first feedback signal can be used for both controlling the first motor accurately, so that the metering chamber is bounded at a certain volume, and for obtaining an accurate indication of the set metering volume when the metering volume is set manually.

In an embodiment of the present invention the assembly comprises a second motor, preferably a servomotor, to drive the piston.

In an embodiment the assembly comprises a second sensor, able to provide a second feedback signal in which position the piston is and/or how much force the motor exerts on the piston. The second feedback signal can also be given by the servomotor. In an embodiment the assembly comprises a control device which is adapted for adjusting the ejection stroke of the piston 1 on the basis of the first and/or second feedback signal. In that way it can at least partially be prevented that the dough is pressurised too much.

An embodiment of the present invention comprises said assembly wherein the control device is adapted for executing an instruction program, placed on a medium, for carrying out an above-mentioned method.

In an embodiment the assembly comprises memory means for storing optimal piston stroke magnitudes and/or other machine parameters for the dough product. These data can be used afterwards by an embodiment wherein the assembly comprises an entering means for entering the recipe and/or machine parameters of the dough product and for selecting piston stroke magnitudes that have previously been stored with previously stored dough recipes. As a result it will no longer be necessary to carry out a piston stroke optimisation for dough types for which the optimal piston stroke has already been stored before.

In an embodiment the entering means of the assembly comprises a touch screen. Said input means is easy to operate and easy to clean.

According to a further aspect the present invention provides a computer program which when loaded in a computer memory comprises program instructions for carrying out the above-mentioned method.

The aspects and measures described in this description and the claims of the application and/or shown in the drawings of this application may where possible also be used individually. Said individual aspects may be the subject of divisional patent applications relating thereto. This particularly applies to the measures and aspects that are described per se in the dependent claims.

SHORT DESCRIPTION OF THE DRAWINGS the method and operation of the assembly will be described more elaborately in the detailed description of the drawings, in which:

Figure 1 a shows a schematic view in cross-section of a dough metering device;

Figure 1 b shows the same dough metering device wherein the piston has been moved to push dough from the suction chamber in the direction of the metering chamber;

Figure 2 shows a dough metering device wherein the metering chamber deposits the metered dough portion onto a conveyor belt in order to be weighed by a weighing device;

Figure 3 shows an example of an entering means, in this case a touch screen, of the assembly, wherein the entering means is adapted for entering and/or selecting parameters for the method for setting the optimal piston stroke magnitude; and

Figure 4 shows a flow chart of the method of the present invention wherein the number of optimisation strokes per piston stroke magnitude is set beforehand.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made to figure 1 a, in which a dough metering device is shown wherein the dough mass is stored in a dough hopper 4 which can be closed off from a suction chamber 5 by a blade member 2. A slide 7 is shown here in a lowermost position as a result of which there is no passage between the metering chamber 6 and the suction chamber 5. The volume of the metering chamber is bounded by a metering piston 3. A first sensor {not shown) is able to give a first feedback signal indicating at which volume the metering chamber has been set. In the suction chamber 5 a piston 1 moves away from the slide as a result of which dough is sucked from the dough hopper into the suction chamber. In figure 1 b the blade member 2 has closed off the connection between the suction chamber 5 and the dough hopper 4. The slide 7 has been moved to an uppermost position as a result of which the metering chamber 6 and the suction chamber 5 connect to each other. A movement of the piston in the direction of the slide pushes, at least a part of, the dough from the suction chamber into the metering chamber. A second sensor (not shown) is able to give a second feedback signal indicating how much force is exerted by the piston, which is also an indication of the pressure to which the dough is exposed. Said second feedback signal can be used to provide feedback to the piston so that the ejection stroke of the piston can be adapted according to wish.

In figure 2 the slide with full metering chamber has been moved to the lowermost position, where the metering pistons eject the metered portion of dough 23 onto a conveyor belt 22 which passes the dough to a weighing device 21. The weighing device comprises means, preferably a photocell, that are used to establish whether there is a dough portion on the weighing device in order to be weighed. When during a predetermined time period, preferably 30 times the cycle time of a portion of dough, no dough products have been weighed by the weighing device, the next piston stroke magnitude is switched to until all piston stroke magnitudes have had their turn and the optimal piston stroke has been found. When the metering device for instance has carried out the metering stokes for a piston stroke magnitude then the metering device (temporarily) stops metering as a result of which after one cycle time at the most, no dough portions end up on the weighing device for a prolonged duration. If for instance there is no more dough in the hopper, the optimisation process according to this method will be completed, wherein it can be indicated that for certain piston stroke magnitudes no dough portions have been weighed.

In figure 3 an exemplary input means of an embodiment of the assembly according to the present invention is shown. The input means in this case is a touch screen with which the number of strokes for optimisation can be set and with which the order can be given for retrieving and/or storing combinations of the piston stroke magnitude and the related other machine parameters for the dough product. In figure 4 an embodiment of the present method is shown in a flow chart. It is possible to let the execution of the method take place by three parts of an assembly for metering dough, wherein the assembly in this case comprises a metering device 400, a conveying device 500, and a weighing device 600. After starting 401 the metering device, the number of metering strokes per piston stroke magnitude is set 402. Said number of metering strokes can be set by a user or automatically.

Subsequently the piston stroke magnitude of the metering device is set to the largest piston stroke magnitude 403 for which the standard deviation of the resulting dough portions has to be determined. After that one piston stroke is carried out 404 of which the resulting dough portion(s) are discharged and ignored by the weighing device. The set number of metering strokes is subsequently carried out 405, after which it is verified whether the smallest piston stroke has already been set 406. If this is not the case, and there still are piston stroke magnitudes for which no optimisation strokes have been carried out then the next largest piston stroke is set and the metering of dough portions is temporarily stopped 407. When the smallest piston stroke magnitude had already been set then for all selected piston stroke magnitudes the standard deviation in weight of the dough portions has been calculated and the piston stroke magnitude which had the smallest standard deviation can be set as the optimal piston stroke magnitude 408, after which the optimisation of the piston stroke magnitude has been completed 409.

During metering the metering device is able to discharge the metered dough via the conveying device (500), which conveys the dough portion(s) to the weighing device (600).

After starting (601 ) the weighing device and starting a new series of dough portions for determining the standard deviation in weight, it is determined, preferably by means of a photocell, whether there is a dough portion on the weighing device (602). If this is the case the dough portion is weighed and discharged (603). When no dough portion has been found it is verified whether at least one cycle time, preferably 30 times the cycle time of a piece of dough from the metering device to the weighing device, has passed by since the last time dough was found on the weighing device (604). Such a time span that no dough Is found on the weighing device occurs for instance when the metering device has finished carrying out the entered number of metering strokes for a piston stroke magnitude.

When said time has passed by without a dough portion having been weighed, the standard deviation in weight of the series of dough portions is calculated and stored 605 and a signal is sent to the control device for starting 606 the metering device so that it starts metering again after which weighing a new series can be started with 404. In between two dough weighings such a signal is sent only once.

Below an example is given of an embodiment of the method according to the invention. It is given that the metering machine has 4 metering chambers and a capacity of 1800 strokes per hour, therefore per hour

7200 pieces of dough can be metered. The number of metering strokes per piston stroke magnitude in this example is set at 4. When starting the optimisation the first 4 products are ignored. The next 16 products {4x4} are weighed and the standard deviation is determined. The metering device is stopped, but the discharge conveyance continues for discharging the products between the metering device and the weighing device. When the metering device has not found products for

30 times the theoretical cycle time (7200 pieces per hour / 3600 seconds per hour) * 30 = 15 seconds, the next largest piston stroke magnitude is switched to and the metering device is automatically started again.

Alternatively it is possible that the control device sets, starts and stops the metering device at predetermined points in time, without the control device first having received a signal from the weighing device that for a certain time no dough portion has been weighed anymore. Assume that setting a piston stroke magnitude takes 5 seconds at the most, and like in the previous example, carrying out one piston stroke takes 1800 strokes per hour / 3600 seconds per hour = 0.5 seconds. Carrying out 4 metering strokes for a piston stroke magnitude, including setting said piston stroke magnitude and carrying out one stoke of which the dough portions are ignored then takes ((4 + 1 ) strokes * 0.5 seconds per stroke + 5) = 7.5 seconds. After carrying out the metering strokes the metering device is stopped and then 15 seconds have to be waited for so that the weighing device knows that the last dough portion for the piston stroke magnitude in question has been weighed.

Therefore 22.5 seconds after having started with setting a piston stroke magnitude, the metering device from the example is able to start with the next piston stroke magnitude, wherein the weighing device has sufficient information at its disposal to be able to calculate a correct standard deviation in weight of the dough portions. An advantage of time-controlled starting and stopping of the metering device is that control lines will no longer be necessary between the metering device and the control device.

In an alternative embodiment both the metering device and the weighing device have counters for the number of metered dough portions and the number of weighed dough portions, respectively. When weighing a portion of dough it is then possible, on the basis of the number of dough portions weighed up until then, to determine with which piston stroke magnitude said portion of dough has been metered. An advantage of using counters is that the metering device no longer needs to be stopped; after metering a number of metering strokes another piston stroke magnitude can be switched to and metering dough portions can immediately be continued with.

The above description is included to illustrate the operation of preferred embodiments of the invention and not to limit the scope of the invention. Starting from the above explanation many variations that fall within the spirit and scope of the present invention will be evident to an expert.

toctrooi/186218/PCTP186218A des BW/NG 4394}