DE10136809A1 - Method for cutting off product from a product loaf, e.g. cheese, sausage, ham, etc. so that the slices have constant weight, involves optical measurement of the cross section area of the product and adjustment of movement speed - Google Patents

Abstract

Method for dividing a product loaf (14) using a cutting machine with a blade (18), which has means for measuring the cross section area of the product loaf so that the advancement speed of the loaf can be adjusted accordingly. The cross section area is measured using a light pattern (64, 68) projected onto the surface with a measurement line used to evaluate the geometry of the cross section. The inventive method can be used to calculated cross section errors so that an adjustment transporter (12) can be used to adjust transport speed so that cut off sections have constant weight.

Description

The invention relates to a method for dividing a Product loaf according to the preamble of claim 1.

Such a method is described in DE 198 20 058 A1 described. In detail, different ones Alternatives for determining the cross sectional area of the Product loaf specified. These include optical ones Procedure, namely the measurement of the area of a cut slice and scanning the loaf surface using a variety of optical Distance sensors. The first alternative is well suited if the cross-sectional area of the product loaf changes in Loaf longitudinal direction does not change too quickly, so that one from the geometry of an already cut disc on the geometry of the following section of the Product loaf can conclude. The second of the addressed The advantage of alternatives is that the Cross-sectional area of the product loaf even before cutting the can measure individual slices or portions and the control of the delivery of the product loaf against the cutting knife depending on the Can perform actual cross-sectional area. Optical distance sensors are but relatively expensive, so the whole Measuring arrangement becomes expensive when you consider the boundary surface of the product loaf with high resolution.

The present invention is intended to provide a method according to the preamble of claim 1 are further developed that one can measure the contour of a boundary surface of the product loaf with high resolution using an optically and mechanically simple measuring arrangement can perform.

This object is achieved by a Method with the features specified in claim 1.

In the method according to the invention one makes use of it Use that when you have a pattern projected geometry onto a surface, there a Brightness pattern, which is compared to a Brightness pattern that is predetermined on a reference surface Geometry is obtained, has deviations. This Deviations can easily be found below Consideration of the projection geometry in the edge contour of a Cross-sectional area can be converted.

The data required for this invoice regarding the Actual brightness pattern and the reference brightness pattern can easily be won with a camera, and the evaluation of the actual brightness pattern can under Use of known methods and programs of the Image evaluation done.

The method according to the invention can thus be used carry out mechanically simple aids in practice a projection device for the measurement pattern and one Camera that shows the actual brightness pattern on the Boundary surface of the product loaf (measurement) or the Reference loaves (calibration) records. The measuring arrangement comprises therefore no mechanically moving parts and very simple and inexpensive construction. Evaluating the Actual brightness pattern can e.g. B. using a PC with interface card for one camera, the is suitably programmed to the reference Brightness pattern and the actual brightness pattern too save (if necessary for a plurality of in the longitudinal direction of the loaf successive measurement levels, provided the reference loaf does not have a constant cross-section in the longitudinal direction of the loaf) and evaluate the measurement line (s).

Advantageous developments of the invention are in Subclaims specified.

The development of the invention according to claim 2 has the advantage that the actual brightness pattern Image of the camera to be measured Boundary surface of the product loaf created, only locally is modified, but is not partially shadowed. This is an advantage if you look for more information the image of the product loaf to control the Wants to use the delivery device. So you can z. B. at Ham sides from the color of the surface infer whether the considered sub-area of the product loaf more or contains less fat, which is the local density of the Product loaf can affect.

Even with the method according to claim 3, the image remains boundary surface of the product loaf to be measured largely preserved.

The development of the invention according to claim 4 has the advantage that you only to generate the measurement pattern very simple and easy with good accuracy manufacturable mechanical elements needed.

The development of the invention according to claim 5 has the advantage of having a full range of boundary surface to be measured or the entire boundary surface of the product loaf can be measured in one step.

It is possible in the method according to claim 6 despite an oblique projection of the measurement pattern onto the Loaf of product on the boundary surface of the To produce loaves of product essentially equidistant measuring lines, also for a more oblique angle of incidence, as in With regard to strong change of position of the lines in the Actual brightness pattern depending on changes in position of the Boundary area to its main extension area vertical direction is an advantage.

The development of the invention according to claim 7 allows in a very simple way also the production of linear ones Brightness pattern using only small amounts of light. On the one hand, this is in terms of energy consumption the measuring arrangement, on the other hand with regard to the Avoid unwanted heating of the product loaf advantageous. Facilities that moved in one plane Generating light rays are right on the market reasonably priced because they B. also in scanners from Barcode readers can be used.

In the method according to claim 8, the measuring line is the to visualize the height profile of a boundary surface of the product loaf is used, the edge of a Used shadows thrown by a ruler plate, or also the image of a line that marks the junction between different colored filter sections. Such ruler plates and two-color filters can be very inexpensive even in large dimensions produce. Their assembly and adjustment is also very simple.

In the method according to claim 9, the changes in the brightness pattern on the product surface, which by fluctuations in the height of the measured Boundary surface are not determined by the observation angle shortened. So you have a high sensitivity of the Height measurement of the boundary surface.

Is used to observe the actual brightness pattern on the boundary surface of the product loaf to be measured a camera oriented according to claim 10, so needs one looks at the image of the Actual brightness pattern is little or no additional To do arithmetic to the observation geometry compensate. Also, a vivid one is straightforward Presentation of the Given the profile of the boundary surface.

The development of the invention according to claim 11 has the advantage that the observation geometry and the Projection geometry in a simple way together be made as a camera and projection head comprehensive measuring head used as a whole in the cutting machine will, e.g. B. at a predetermined attachment point, the Has mating surfaces is attached. With that you also have after that to be done on food slicers regular thorough cleaning, for which the exposed machine parts are regularly dismantled the same measurement conditions again.

The invention based on Exemplary embodiments with reference to the drawing explained. In this show:

Figure 1 is a schematic side view of a cutting machine for product loaves with an integrated measuring arrangement for measuring the actual cross-sectional area of the product loaf in the vicinity of a cutting disc, the product loaf and two belt conveyors of the cutting machine are shown obliquely from above.

Fig. 2 is a schematic representation of a reference loaf that is illuminated by an oblique parallel light beams using a ruler plate;

Fig be illuminated 3 to 5 are views similar to Figure 2 but in which the product loaves with deviations having Direction upper boundary surface using the ruler plate..;

Fig. 6 is a schematic perspective view of a loaf product which is moved on an infeed conveyor to a rotary cutting disc, as well as a measuring arrangement for calculating cross-section; and

Fig. 7 is a schematic representation of a modified measuring arrangement for measuring the contour of an upper boundary surface of a product loaf.

Fig. 1 shows schematically the most important assemblies of a cutting machine with which long loaves of product (cheese loaves, sausages, ham sides and the like) are broken down into slices or portions. The cutting machine comprises a cutting head 10, an infeed conveyor 12, on which a Produktlaib 14 is delivered to the cutting head, and a discharge conveyor 16, on which generated by the cutting head 10 stacks of product slices or from the cutting head 10 separated portion pieces from the cutting machine away to a subsequent weighing station and packaging station are promoted.

The cutting head 10 comprises a cutting knife 18 with a spiral cutting edge 20 , which sits on a knife shaft 22 . The knife shaft 22 is supported by a bearing 24 in the bearing plate 26 , which is firmly connected to a main frame 28 of the cutting machine, which is only schematically indicated. The knife shaft 22 is driven by an electric drive motor 30 with the interposition of a belt transmission (not shown in the drawing) at high speed (in the order of 1000-3000 rpm).

Furthermore, the cutting head 10 comprises a strip-shaped counter knife 32 which is carried by the main frame 28 . The end face of the counter knife 30 on the left in FIG. 1 is closely adjacent to the cutting plane S of the cutting head 10 predetermined by the cutting edge 20 , as is required for cooperative cutting in such machines.

The feed conveyor 12 comprises two deflection rollers 34 , 36 , over which a conveyor belt 38 runs. The upper run of the conveyor belt 38 is supported in the vertical direction by a guide plate 40 . The downstream deflection roller 34 is adjacent to the counter knife 32 and is driven by an electric drive motor 42 . The movement of the conveyor belt 38 is measured using an angle encoder 44 , which is coupled to the drive motor 42 .

The discharge conveyor 16 has, in addition to an upstream deflection roller 46, a downstream deflection roller (not shown in the drawing). A conveyor belt 48 runs over these deflection rollers. A drive motor (not shown in the drawing) is provided for one of the deflection rollers of the discharge conveyor 16 .

Among the product loaves, as they are processed on the cutting machines considered here, there are also those in which the cross-sectional area changes in the longitudinal direction of the loaf. In order to ensure, despite such a change in cross-section, when assembling the disc stacks or when cutting off the individual portion pieces that these have the desired total weight, a measuring arrangement is additionally provided in the cutting machine shown in FIG. 1, which measures the actual cross-sectional area of the product loaf.

This measuring device comprises a projection head 50 , which is arranged behind the cutting knife 18 , seen in the conveying direction of the product loaves, a ruler plate 52 , which is arranged shortly behind the cutting knife 18 between the latter and the projection head 50 , and a camera 54 , which is upstream of the cutting knife 18 is arranged.

The ruler plate 52 is shown here as attached to the bearing plate 26 . Its lower edge extends in a direction that is parallel to a feed plane Z, in which the underside of the product loaf 14 is moved against the cutting head 10 , and perpendicular to the loaf feed direction. In the exemplary embodiment considered here, the infeed plane Z is predetermined by the upper run of the conveyor belt 38 , which is supported by the guide plate 40 .

The projection head 50 generates a parallel light curtain 56 which is substantially homogeneous in the direction perpendicular to the drawing plane of FIG. 1. The extent of the light curtain and the ruler plate in the direction perpendicular to the drawing plane of FIG. 1 is so great that the light curtain and ruler plate can cover the width of all product loaves to be cut with the cutting machine under consideration.

As can be seen from FIG. 1, the position of the lower edge of the ruler plate 52 and the angle of attack of the projection head 50 and thus of the light curtain 56 are selected such that the lower edge of the ruler plate 52 on the upper boundary surface 58 of the product loaf 14 when the Product loaf 14 has a predetermined ideal shape (here a rod with a rectangular cross section) in which the cutting plane S lies.

The direction of the light curtain 56 is indicated at P in the drawing. This direction is called the projection direction for short.

The camera 54 is arranged in front of the cutting head 10 at such a height and at such an inclination that the axis of its objective (direction of observation) with respect to the cutting plane S runs symmetrically to the direction of the light curtain 56 .

A control unit 60 controls and energizes the drive motors 30 and 42 and the projection head 50 . The control unit 60 receives as input signals the images generated by the camera 54 of the end section of the product loaf 14 immediately adjacent to the cutting plane S and the output signal of the angle encoder 44 , which is a measure of the relative position between the product loaf 14 and the cutting plane S.

The measuring arrangement formed by the projection head 50 , the ruler plate 52 , the camera 54 and an evaluation circuit 62 of the control unit 60 allows deviations of the product loaf 14 from the ideal geometry to be recognized and these deviations to be taken into account when controlling the feed of the product loaf 14 in such a way that the cut-off slices have a constant weight despite deviations in the cross-sectional area.

The principle of measuring the cross-sectional area will now be explained with reference to FIGS. 2 to 5:
Fig. 2 shows the product loaf from the point of view of the camera. On the upper boundary surface 58 of the loaf of product one can see a shaded dark surface area 64 and an illuminated bright surface area 66 , which are separated from one another by a line 68 which is generated by the lower edge of the ruler plate 52 . Line 68 runs exactly transversely to the longitudinal direction of the product loaf.
In FIG. 2, the image of the described surface area of the product loaf 14 is indicated schematically at 70, which is determined by the camera 54 and transmitted to the evaluation circuit 62 .
Fig. 3 shows the same conditions, but now a portion of the product loaf 14 is at the measuring point, which has a reduced height. The actual shape of the product loaf is shown by solid lines. The conditions for the ideal geometry of the product loaf are entered for comparison by dashed lines. It can be seen that the line 68 in the camera image 70 has migrated downwards, and the extent of the downward migration after the radiation set can be converted directly into the reduction in the height of the product loaf. It goes without saying that a product loaf section which is higher than the ideal geometry of the product loaf leads to line 68 in the camera image moving upward.
Fig. 4 shows the situation in the event that the upper boundary surface 58 of the product loaf 14 is not parallel to the lower boundary surface. It can be seen that the inclination of the upper boundary surface 58 leads to a corresponding tilting of the line 68 in the image 70. The inclination of the boundary surface 58 can again be calculated from the tilting of the line 68 in the image 70, taking into account the simple imaging geometry.
FIG. 5 shows the conditions in the upper boundary surface of a product loaf section which has a groove-shaped upper recess 72 . The contour and depth of the depression 72 can again be determined from the line 68 , which lies in the camera image 70 between the dark area 64 and the light area 66 .

The irregularities in the product loaf geometry that occur in practice can be accomplished in a simple approximation as a superimposition of the surface irregularities described above. On closer inspection, the back calculation from line 68 to the edge contour of the cross-sectional area would have to take into account that the surface irregularities of the boundary surface 58 are not constant in the longitudinal direction of the loaf. This can be done with increased computing effort (taking into account the already determined part of the boundary surface), but is not necessary for many practical cases, since the profile changes on ham sides, cheese loaves and the like are often gentle in the longitudinal direction of the loaf.

In the method described above, the deviation of the position, orientation and shape of a shadow line was used to measure the contour of the boundary surface 58 . It goes without saying that lines can also be used for the same purpose which are dividing lines between other differently illuminated surface sections.

So you can use a semi-transparent mirror instead of the ruler plate 52 so that the surface area 64 is not completely without measuring light but only receives a smaller amount of measuring light.

Again, optionally, a filter of the same geometry can be used instead of the ruler plate 52 so that the surface area 64 is colored and the surface area 66 is illuminated with white light.

In a further modification, a double filter can be provided in the projection head 50 , which is colored differently in its two halves colliding along a straight line, so that there are two differently colored surface areas 64 , 66 on the upper boundary surface 58 . In all of these cases, the line 68 is retained as such and allows the contour of the boundary surface 58 to be observed.

In a further modification, the trace of a light beam can be used as the measuring line, which is moved in the transverse direction over the upper boundary surface 58 . A corresponding measuring arrangement is shown in Fig. 6. Parts of the cutting machine and the measuring arrangement, which have already been explained with reference to FIGS . 1 to 5, are again provided with the same reference numerals. These parts need not be described again in detail below.

In the measuring arrangement shown in FIG. 6, a laser 74 is used, which generates a light beam 76 directed obliquely downward to the boundary surface 58 . A prism 78 is arranged in the path of the light beam and is rotated by an electric drive motor 80 about an axis perpendicular to the axis of the light beam 76 . The light beam 76 is deflected by the circumferential prism 78 and a bright line 82 is obtained on the boundary surface 58 .

Units that have such a flat fan of light are known as assemblies in barcode scanners, with a deflecting mirror instead of a deflecting prism or use mirror drums.

In the measuring arrangement according to FIG. 6, the camera 54 is likewise arranged in the half space lying in front of the cutting plane S, preferably perpendicularly above the point at which the line 82 is generated with the ideal geometry of the product loaf.

As can also be seen from FIG. 6, the optical and mechanical parts of the arrangement for measuring the cross-sectional contour of the product loaf are arranged at a distance in front of the cutting plane S in the conveying direction. In view of this, it is advantageous to keep contaminants that inevitably arise during cutting away from the measuring arrangement. DE 98 20 058 A1, already mentioned at the beginning, describes how the measurement results of a measuring arrangement, which is (also a larger distance) from the cutting plane S, are used with the interposition of a memory which is addressed by the angle encoder 44 . to keep the weight of the slices cut off essentially constant. In this regard, reference is made explicitly to DE 198 20 058 A1.

In the above described embodiments of the Produktlaib 14 was continuously measured with the delivery to the cutting head 10 by moving past the measuring arrangement. Alternatively, the entire loaf of product can also be measured by a single spatially extended measurement, as will now be described with reference to FIG. 7. Parts of the measuring arrangement which have already been described above are again provided with the same reference symbols.

In the measuring arrangement according to FIG. 7, a transparent template 84 with a measuring pattern is arranged inside the projection head 50 , which is drawn out separately in FIG. 7. The template 84 comprises a plurality of longitudinally successive line-like inhomogeneities or lines 86 (scratched lines, raised lines, printed color lines). The size of the template 84 is dimensioned such that the light curtain 56 generated by the projection head 50 extends over the entire length of the product loaf 14 .

The light curtain 56 is again directed against the product loaf at an oblique angle. In order to obtain equidistant lines 68 on the upper boundary surface 58 despite this projection geometry, the lines 86 on the template 84 are not arranged equidistantly but in such a way that the line arrangement compensates for the projection geometry, as indicated schematically in the drawing.

The camera 54 is again arranged above the upper boundary surface 58 . This simultaneously captures all measuring lines 88 , which are each an image of one of the lines 86 .

The surface contour of the boundary surface 58 can be determined by evaluating the deviation of the position and geometry of the individual lines 88 , which are obtained with a product loaf under consideration, from those lines which are obtained with a reference loaf.

For this purpose, the evaluation circuit 62 contains two image memories 90 , 92 on the input side, which can optionally be connected to the output of the camera 54 via a switch 94 . The changeover switch 94 is moved into a dashed calibration position to the right in FIG. 7 for measuring a reference loaf, into a left working position for measuring the irregular product loaves to be cut.

A computing unit 96 , which in practice can be formed by a freely programmable computer and a corresponding work program for it, is loaded with the two images which are contained in the image memory 90 , 92 . In principle, as described above, the arithmetic unit 96 calculates the cross-sectional contour of the product loaf at the various points in succession in the longitudinal direction of the product, which correspond to the lines 68, from the coverage errors in the two images. It has proven to be sufficient in practice if the distance between the lines 68 is selected to be approximately 0.5 cm.

The computing unit 96 can then calculate the cross-sectional area from the determined cross-sectional contours and store it in a cross-sectional area memory 98 for each longitudinal section of the product loaf. This is controlled by the arithmetic unit 96 for reading in, for reading out as a function of the output signal of the angle encoder 44 , which has been modified in a suitable manner by an addressing circuit 100 (in the case of incremental angle encoders, the counting pulses are added up, otherwise digitization and scaling of the output signal).

The signal available at the output of the cross-sectional area memory 98 is used in a feed control circuit to set the feed of the feed conveyor 12 so that the product of the feed speed and the cross-sectional area is a constant.

If one considers the projection geometry and the observation geometry in the method described above, it is clear that given the deviation between the actual geometry and the desired geometry, the greatest change in position in the measuring lines 68 , 82 , 88 is obtained when the direction of observation is essentially perpendicular the projection direction. Since electronic cameras with a CCD image converter now have a very high resolution and camera optics of high resolution for CCD image converters are not available at too high a cost, cameras that could reliably detect even small changes in position in a line 68 can be obtained at a low cost realize.

This makes it possible to put such measuring arrangements into practice use where the angle between Projection direction P and observation direction B clearly below 90 ° lies. An arrangement in which camera and Projection head are adjacent to each other and to one unit are connected, with regard to that of the measuring arrangement space required in the cutting machine and with regard on a simple joint installation and removal of the optical parts of the measuring arrangement is advantageous. Such one Installation and removal is usually with regard to that daily in-depth cleaning of cutting machines from Advantage. The union of camera and projection head to one unit also creates permanent reproducible Measurement conditions.

A camera 54 adjacent to the projection head 50 is shown in broken lines in FIG. 7.

With the measuring arrangements described above it is over the length of the measuring line (s) also possible, fluctuations in the to measure the clear width of a product loaf. There right now for non-industrially manufactured loaves such as Ham sides the height of the side surfaces significantly smaller than the width of the upper boundary surface, is sufficient it often just the clear width of the product loaf to be taken into account in the feed control and Undercuts in the side surfaces are not taken into account to let.

Where a contouring of the side surfaces is so strong that it must be taken into account, the same measuring arrangements can be provided for the side surfaces as were described above for the upper boundary surface 58 . The cross-sectional areas are then calculated taking into account the upper and the lateral boundary lines.

In many cases it is not necessary to consider profiling the underside of a product loaf, since the product is generally somewhat compliant and adapts under its own weight to the level-supported work strand of the delivery conveyor 12 .

If you also want to measure the lower boundary surface for hard products contoured on the underside, you can provide a somewhat larger distance between the delivery end of the delivery conveyor 12 and the counter knife 32 or use two short delivery conveyors spaced apart in the conveying direction and another one in the section of the underside of the loaf that is then accessible Provide a measuring arrangement as described above.

Are several measuring arrangements for measuring different Boundary surfaces are used, so these are preferred at different ones spaced apart in the longitudinal direction of the loaf Set the product loaf used to a mutual Exclude influencing the measurements. The Taking into account the different positions of the Calculation arrangements can be carried out similarly to those in the DE 198 20 058 A1 for taking into account the distance between Cutting plane and measuring arrangement described.

Alternatively, you can use the various measuring arrangements Operate light of different colors.

In the above-described embodiments the cross-sectional measuring arrangement in the cutting machine. The measuring arrangement can also outside of Be arranged cutting machine. How then those won offline Surface data used to control the loaf feed can be described in DE 198 20 058 A1 which is explicitly referred to again in this regard.

When using an external measuring station you can different boundary surfaces of a product loaf also with measure a single measuring arrangement by the Product loaf in succession in different orientations (Rotating around its longitudinal axis) with the measuring arrangement.

Claims (11)

1. A method for dividing a product loaf ( 14 ) in a cutting machine, which has a moving cutting element ( 18 ) and a device ( 12 ) for delivering the product loaf ( 14 ) against the cutting element ( 18 ), in which the cross-sectional area of the product loaf in one A plurality of longitudinally spaced transverse measurement planes is optically measured and the speed at which the product loaf ( 14 ) is moved against the cutting element ( 18 ) by the feed device ( 12 ) is controlled as a function of the measured size of the cross-sectional area, characterized in that that a light pattern ( 64 to 68 ; 82 ; 88 ) of a given geometry is projected onto the product loaf ( 14 ), which comprises at least one measuring line ( 68 ; 82 ; 88 ) of a given geometry and that is obtained on the product loaf ( 14 ) to be measured Brightness pattern with an observation direction (B) different from the projection direction (P) a reference brightness pattern is compared, which was obtained using the same light pattern and the same projection conditions and observation conditions from a reference loaf of known cross-sectional geometry. 2. The method according to claim 1, characterized in that that the light pattern has at least two areas different color and / or different intensity having. 3. The method according to claim 1, characterized in that the light pattern has at least one shadow line ( 88 ) or a light line ( 82 ). 4. The method according to claim 3, characterized in that the shadow stroke ( 88 ) is obtained by projecting a linear optical inhomogeneity ( 86 ) onto the product loaf ( 14 ), which is selected from the following group: a thin rod, a wire , incised or raised or printed lines on a transparent substrate. 5. The method according to claim 4, characterized in that a light pattern is used which has a plurality of measuring lines spaced apart in the longitudinal direction of the product ( 88 ). 6. The method according to claim 5, characterized in that the measurement lines ( 88 ) are generated by projecting a template ( 84 ) at an oblique angle to the longitudinal axis of the product loaf ( 14 ), wherein the template ( 84 ) has lines ( 86 ), such are not arranged equidistantly so that the image of the template produced on a reference loaf contains equidistant measuring lines ( 88 ). 7. The method according to claim 3, characterized in that the measuring line ( 68 ) is generated by moving a light beam ( 76 ) in the longitudinal direction of the product loaf ( 14 ) transverse direction. 8. The method according to claim 1, characterized in that the measuring line ( 68 ) is generated by areal illumination of a ruler plate ( 52 ) or filter plate. 9. The method according to any one of claims 1 to 8, characterized in that a camera ( 54 ) is used to observe the brightness pattern generated on the product loaf ( 14 ), the optics of which have a perpendicular to the projection direction (P) axis (B) , 10. The method according to any one of claims 1 to 8, characterized in that a camera ( 14 ) is used to record the brightness pattern generated on the product loaf ( 14 ), the optics of which have an axis perpendicular to the longitudinal direction of the product loaf ( 14 ). 11. The method according to any one of claims 1 to 10, characterized in that a camera ( 54 ) is used to observe the brightness pattern generated on the product loaf ( 14 ), which is rigidly connected to a projection head ( 50 ) which generates the light pattern.