Method and Apparatus for Intermittently Dispensing Flowable Foodstuff

This invention relates to a method and an apparatus for intermittently extruding a prepared, flowable sausage mass or the like into suitable containers or casings in predetermined quantities. The extrusion steps alternate continuously with separation steps to separate the last-extruded portion from the following portion. As each extrusion step is terminated by decelerating the sausage means, a trailing or terminal mass or quantity of sausage material flows into the last-extruded portion.

Generally speaking, such apparatus and methods are known to have, for example, an intermittently operated screw conveyor which incrementally advances with a constant angle of rotation. The conveyor is rotated via an electromagnetically actuated coupling/brake combination that has a predetermined operating cycle. During each operating interval, a control device engages the coupling, measures the angle of rotation covered during the operating interval and, after a predetermined angle of rotation has been reached, disengages the coupling and brakes the conveyor to a standstill. The casing section adjoining the last-filled portion is thereupon severed by twisting it off. Thereafter, the next filling step commences, and so forth.

A disadvantage of the known method and apparatus is that the terminal quantity of sausage mass conveyed into the last-filled portion during the braking is not adequately controlled, that is it is only very roughly accounted for when adjusting the desired volume of a portion, since the chronological progress of the braking step cannot take account of the terminal volume of quantity of sausage material conveyed during the braking step. Given a constant load, stable temperature conditions and a correct mechanical condition and adjustment of the apparatus, it is possible to estimate the volume of terminal mass and to trigger the braking step so that the volume of sausage material conveyed up to the commencement of the braking step and the subsequently still flowing terminal mass are substantially equal to the desired volume of the portion. However, under a variable load, unstable temperature conditions and/or changes in the speed of the conveyor screws, the terminal mass and, therefore, also the size of the whole portion fluctuate.

It is therefore an object of the invention to provide a method and an apparatus of the type indicated above which insures that the selected portion volume remains substantially constant even over extended operating times and despite fluctuating load, temperature and/or speed conditions.

This is accomplished in accordance with the invention in that the terminal mass or quantity of sausage material delivered during decelleration of the preceding extrusion step is acertained and that the difference between the size of the portion and the measured terminal mass is established. The braking or decelleration of the actual dispensing step is then initiated when the amount of sausage material actually extruded equals that difference.

The apparatus of the invention comprises a conveyor which is operated intermittently and dispenses a desired volume of sausage material into containers or casings. The apparatus may include a device for separating the last-dispensed portion from the next portion. It further includes a control device comprising a selector for dispensing the desired portion volume, a device for measuring the volume dispensed during the individual filling cycles of the apparatus, and a trigger which triggers braking of the conveyor when a specific volume has been dispensed. If necessary it also triggers the next operating cycle of the conveyor.

During braking of the conveyor, the terminal volume of sausage material flows into the last-dispensed portion. The apparatus of the invention is characterized in that the measuring device includes means for ascertaining the volume of the terminal mass and in that a subtraction device is provided which forms the difference between the predetermined volume of sausage material that is to be dispensed into a container or casing and the measured terminal mass, and which stores that difference. Further, the trigger initiates the braking of the conveyor when the measured, actually dispensed volume during an operating cycle equals the stored volume difference.

The advantages of the invention reside in particular in that the actual amount of the terminal mass is ascertained during the braking phase of one or more preceding dispensing steps and that during the ongoing dispensing step braking is triggered when the dispensed sausage material conveyed during such dispensing step equals the desired portion size less the previously ascertained terminal mass. During the following braking step the terminal mass is substantially equal to that measured during the preceding cycle, which was deducted from the dispensing step, so that the terminal mass substantially completes the dispensed amount, resulting in the desired portion size.

The size of the whole portion, of the terminal mass and of the dispensed sausage material can be measured by weighing, that is, in the form of the corresponding weights. Preferably, however, they are measured by volume of the portion, of the terminal mass and of the dispensed material since, in contrast to measuring by weight, measuring by volume poses no problem even under the generally high frequency at which the dispensing steps take place.

The volume of the terminal mass is preferably determined during braking of the immediately preceding dispensing step. The probability that the volume of the terminal mass during the next cycle is equal to the just measured volume is relatively high, since long-term fluctuations in the load, the temperature, and so forth are thereby eliminated.

Alternatively, the volume of the terminal mass may be determined as the mean value derived from a plurality of individual values which are measured during braking of a predetermined number of preceding dispensing steps, thus also eliminating statistical fluctuations.

The dispensing step preferably comes to a standstill at the end of the braking step. The separation step starts shortly before the end of the extrusion dispensing and is braked, for example, when the next dispensing step starts, so that there is a certain overlapping between the dispensing steps and the separation steps.

In the apparatus of the invention the conveyor is preferably a rotary pump and is driven intermittently via a coupling and an associated brake. The measuring device has a converter which measures the angle of rotation of the pump and emits a number of electric output signals proportional to the angle of rotation. The devices for ascertaining the volume of the terminal mass are disposed in series with the converter and ascertain the volume of this quantity as a corresponding number of output signals of the converter. This results in a conversion of the measured magnitudes into corresponding digital signals. It is then of advantage to digitally set the desired volume of the portions with a selector, for example in the form of a specific count, since the entire control device can then be an electric circuit.

In regard to the hardware, the desired operations may be carried out with an interval counter which may be programmed by the selector. The interval counter receives the output signals of the converter as counting pulses and counts them over a counting interval that is predetermined by the selector and corresponds to the desired volume of a portion. At the end of the counting interval, the counter resets itself to the start of the interval and simultaneously emits a trigger pulse for braking the conveyor pump. After resetting, the counter receives a number of pulses corresponding to the actual volume of the terminal mass, whereby the interval is reduced by an amount corresponding to the volume of the terminal mass. When the next dispensing step commences, the counter subsequently continues to count in the same direction. It reaches the end of the interval when, during the actual dispensing step, the converter has fed to the counter a number of pulses which is equal to the interval minus the volume of the terminal mass, that is, when the conveyor has dispensed a volume of sausage material that is diminished by the volume of the terminal mass. The braking of the conveyor is then triggered. The terminal volume of the sausage material flowing during this braking step then increases the size of the portion to the desired or predetermined size.

When the sausage material is filled into a tubular casing, the separator is preferably a twisting device or a clipping machine which tightly constricts the section of the casing adjoining the filled portion. When filling the sausage mass into different containers, other suitable separator devices may be used, for example conveyors for the container or the like.

FIG. 1 is a sequence diagram illustrating the operational steps of the present invention;

FIG. 2 illustrates a first embodiment of the apparatus of the present invention; and

FIG. 3 illustrates a second embodiment of the apparatus of the present invention.

FIG. 1 chronologically illustrates the sequencing of an apparatus constructed according to one embodiment of the invention to fill a sausage mass into a tubular casing (not separately shown). The apparatus has, for example, a screw conveyor with at least one rotating conveyor screw for transporting the sausage material, and a separator in the form of a twisting device. Shown is the change between conveyor filling or dispensing steps 23 and the separating steps or intervals 24. After a short acceleration time t.sub.2 --curve section AB--the desired rate of rotation of the screw conveyor is reached and maintained during the conveyor filling step 23, curve section BC. The conveyed volume during the operating interval up to the time point C is represented by the surface ABCE obtained by integration of the curve between A and C, and by summing the revolutions of the conveyor screw up to point C. At point C, rotation of the conveyor screw is braked and, after a short decelleration time t.sub.3, it comes to a standstill at the point D. During the braking interval, a terminal volume of sausage material, represented by the surface determined by the points CDE, enters the casing and is added to the just dispensed sausage material. Since the braking step cannot be controlled by the control device, it must be triggered when the volume dispensed up to the time when braking commenced corresponds to the desired volume of the portion minus the volume of the terminal mass. Thus, during the braking interval, the terminal mass brings the whole dispensed sausage material to the desired volume.

Before a complete standstill of the conveyor screw is reached, at point D, the twisting device is actuated which, after a short starting phase, twists the casing section adjoining the last-filled portion over a predetermined period of time and with a predetermined speed to thereby replace the just filled casing, or section of a casing, with a fresh casing section that is to be filled during the next operating cycle. The twisting device is deactivated and comes to a standstill after a short deceleration phase. Simultaneously with the deactivation of the twisting device, the conveyor screw is again energized, at point A', and it goes through the next operating cycle A'B'C'D'. The cycle interval t.sub.1 from the start of a complete operating cycle to the start of the next complete cycle may be decreased by overlapping of the filling steps or intervals 23 with the separation intervals 24. The cycle interval t.sub.1 and the pause time t.sub.4 -from the standstill of an operating interval to the commencement of the next operating interval-can be selected. The same applies to the rates of rotation.

FIG. 2 shows a first embodiment of the apparatus constructed in accordance with the invention for dispensing a sausage material into a tubular casing. A conveyor pump 2 has two cooperating conveyor screws 3 and is intermittently coupled to a continuously operating drive via an electromagnetically actuated coupling 4. During the filling steps, the pump conveys a sausage material into a tubular casing which is mounted over an output spout of the pump. The sausage mass is dispensed into the tubular casing in portions of the desired volume.

A twisting device 22 twists off the empty casing section adjoining the last-filled section thereof as soon as a control device 1 terminates the filling cycle by deactivating the conveyor screws 3 and energizes the twisting device, in accordance with the sequencing illustrated in FIG. 1. A measuring device 6 includes a converter 7 operatively connected with the driven end of the coupling shaft which measures the angle of rotation of the conveying screws 3 and transforms it into a number of electric output signals proportional to the angle of rotation. The output signals emitted within any time interval are a measure of the volume which was conveyed by the pump and dispensed into the casing during such time interval.

An interval counter 7a is mounted in series with converter 7. Its counting interval is programmed by a selector 14 so that it corresponds to the desired volume of the portions to be dispensed by the conveyor pump 2. The selector device may, for example, comprise a decade switch or a keyed input which is followed by an interim memory. The trigger 18 has a first output connected with the electromagnetic control of coupling 4 and a second output connected with the twisting device 22. The entire control device 1 is activated or deactivated with a toggle switch 20 which is also connected to trigger 18.

A device 8 for determining the volume of the terminal mass precedes interval counter 7a and can be connected therewith by means of reversal switches 12. The device 8 comprises an averager 9, a pulse generator 10 and a control logic 11. The pulse generator is connected with the averager 9 and the control logic 11 and serves for adjusting the stored mean value in the interval counter 7a . At the correct point in time, the control logic 11 reverses switches 12 into their first position, in which the interval counter 7a is directly connected with converter 7. During each braking interval, the control logic 11 connects the device 8 to converter 7 for measuring the volume of terminal mass. An average of a predetermined, constant number of measured terminal volumes which immediately preceded the operating cycle in question, together with the last measured terminal volume is then formed into a new mean value in the averager 9 and kept available as the "measured volume of the terminal mass".

In operation, the counter 7a receives counting pulses and counts through the counting interval as set by the selector 14 and which corresponds to the desired volume of sausage material to be dispensed At the end of the counting interval, the interval counter 7a emits a trigger pulse to the trigger 18. Simultaneously, the trigger emits a braking signal to the control of the coupling 4 to terminate the filling step. At the same time the counter 7a resets itself to the beginning of the counting interval. During the braking interval, which is now in progress, the device 8 is connected to converter 7, counts the volume of the terminal mass and with it updates the mean value of the measured volume of the terminal mass. As soon as the updated mean value is available, which occurs in the pause following the last filling step, the control logic 11 connects the averager 9 with the interval counter 7a, and sends to the interval counter 7a a number of counting pulses corresponding to the mean value of the measured volume of the terminal mass. The counting interval for the next filling cycle is thereby shortened by the mean volume of terminal mass.

Prior to the start of a new filling step, the counter 7a is directly connected to converter 7. It then counts the output signals of the converter which correspond to the volume dispensed by the conveying pump from the beginning of the next filling step. At the end of the counting interval, a new trigger pulse is emitted to brake the conveyor screw 3, and the counter again resets itself. During the braking interval, the device 8 updates the mean value of the measured volume of the terminal mass.

In this new cycle, braking of the filling step at point C is triggered after the lapse of a counting or time interval which is shortened by the measured mean volume of the terminal mass. During the following braking interval, the trailing mass flows into the just dispensed portion of sausage material to thereby bring the whole portion of sausage material to the desired volume.

FIG. 3 illustrates another embodiment of the invention which substantially corresponds to the embodiment of FIG. 2, but which operates without averaging the volume of the terminal mass. Instead it keeps available, as the actual volume of the terminal mass, the volume measured during the braking step of the preceding operating cycle.

In the embodiment shown in FIG. 3, the counting interval which corresponds to the desired volume of the sausage material to be dispensed and which is set with selector 14 is programmed into the interval counter 7a. At the end of the counting interval, the counter triggers a pulse to brake the conveyor screws 3 and simultaneously resets itself to the start of the next counting interval. The interval counter 7a is continuously connected with the converter 7 of the measuring device 6. Immediately after resetting, that is, after the braking step has been triggered, the counter 7a receives from the conveyor 7 a number of pulses corresponding to the measured volume of the terminal mass. The predetermined counting interval is thereby shortened by the just measured terminal volume. When the next filling cycle begins, the interval counter 7 counts the shortened interval fully and then emits a trigger pulse for braking the screw 3 and again resets itself. Thus, up to the braking point, an amount is conveyed during the filling step which corresponds to the volume difference (shortened counting interval) between the desired volume of the portion to be dispensed (predetermined counting interval) and the volume of the terminal mass. The desired volume of the portion is attained during the braking step with the terminal volume.

In the embodiments of FIGS. 2 and 3, the interval counter 7a fulfills the function of a subtracting device which subtracts the terminal volume (number of counting pulses counted during the braking interval) from the desired volume of the portion (predetermined counting interval) and thus produces the shortened counting interval. In the embodiment of FIG. 3, the interval counter 7a also performs the function of the device 8 (shown in FIG. 2) for ascertaining the terminal volume; a separate device 8 is not required in this embodiment.

The conveyor pump 2 may also be a wing cell pump or an axial piston pump.