GB2239787A

GB2239787A - Apparatus for portioning meat for sliced packs

Info

Publication number: GB2239787A
Application number: GB9100546A
Authority: GB
Inventors: John Arthur Whitehouse
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-01-12
Filing date: 1991-01-10
Publication date: 1991-07-17
Anticipated expiration: 2011-01-10
Also published as: GB2239787B; GB9000681D0; GB9100546D0

Abstract

In a meat slicing apparatus for removing slices from the face of a body of meat ready for incorporation into sliced packs of predetermined weight, the surface area of the face of the body of meat is determined by the operation of scanning means, the thickness of a portion required to produce the predetermined weight is computed, the mean slice thickness required to produce a given number of slices of equal thickness from said portion is calculated, and the apparatus is operated to cut said number of slices of calculated mean thickness from the face of the body. The body 2 of meat is moved incrementally to a rotating cutter 3 and the cut slices (or the face of the meat) are scanned at 4 to determine the surface area, the thickness of a portion required to produce the predetermined weight is computed from the surface area and the density, and required number of slices of equal thickness are cut and check-weighed at 32 to produce an error signal. The cutter 3 is a spiral or hypocycloidal knife. The scanner may be incorporated into the knife. <IMAGE>

Description

Title: Apparatus for portioning meat for sliced packs Field of the Invention The invention relates to apparatus for portioning sliced meat.

Background to the Invention Our US Patent No 4603610 and UK Patent No. 2149650, for example, describe apparatus designed to cut chops, steaks and like products which are partly or completely frozen, and possibly contain bone. Such portions are typically between lOmm and 30mm thick, with weights in the range 80 to 250 grammes. The apparatus employs a bandsaw as its cutting tool in order to cope with the hardness of frozen or bone-in product.

The known apparatus includes a digital scanning system which is capable of performing a simple but fast twodimensional scan of the face of the product to be cut and to compute the surface area of the next portion, regardless of its shape. This enables the machine to automatically adjust the thickness of each slice before it is cut, in order to produce portions all containing the same volume of product, even when the raw material varies randomly in cross-section, as is the case with a pork loin or a whole salmon. Comparison of the actual weight of the cut portions with the demanded weight input to the APC computer by the operator, produced an error signal. This error signal is used to adjust a control factor (density) which enables the apparatus to relate portion volume to portion weight.This results in a 'closed-loop' control system for 'portion control' cutting of equal weight portions from raw material of irregular cross-section.

It would be advantageous to apply a similar control system to the cutting of unfrozen boneless product in thin slices, such as bacon or luncheon meat.

In this case, the use of bandsaw is not necessary and the process is typically performed by rotary or planetarymotion knife slicers. Whilst these knife slicers do not normally have the weight control capability of the known apparatus above described they do not lose product in 'sawdust' due to use of a bandsaw cutting tool.

The invention According to the present invention, in a meat cutting apparatus employing a knife slicer, for removing slices from the face of a body of meat ready for incorporation into sliced packs of predetermined weight, surface area of the face of the body of meat is determined by the operation of scanning means, the thickness of a portion required to produce the predetermined weight is computed, the mean slice thickness required to produce a given number of slices from said portion is calculated, and the apparatus is operated to cut said number of slices of calculated mean thickness from the face of the body.

Preferably, the pack weight incorporating said number of slices is compared with the required pack weight and an error (density control) signal fed back back so that any weight error is corrected when the next predetermined number of slices are cut.

Several known types of conventional knife-based slicers could be employed:1. The power cleaver A system in which product is conveyed in a circular path in a series of vertical magazines across a circular knifeedge blade itself rotating about a vertical axis. These machines are capable typically of 120 alices per minute.

2. The orbital slicer A system in which a single 'log' of product is fed in discrete steps through an aperture which opening is periodically passed by a circular knife-edge blade. In this system the knife undergoes compound rotation, rotating about its own axis whilst simultaneously rotating eccentrically to provide the intermittent 'slicing' action. In these machines the single log of product is fed through the aperture vertically or slightly inclined to the vertical. Such systems are capable of maximum slicing rates typically of 1200 - 1500 slices per minute.

3. The rotary knife slicer A system in which a single 'log' of product is fed horizontally through an aperture which is periodically passed by a spiral or hypo-cycloidal knife rotating about a horizontal axis. Such machines are capable of maximum slicing rates typically of 1000 - 1200 slices per minute.

Probably the most suitable for implementation of the present invention is the rotary knife slicer. It is to be noted that the slicing rate of these types of machines is directly related to the slice thickness. In production requiring large slice thicknesses, the time required to feed the 'log' of product through the aperture is such that the rotational speed of the blade has to be reduced.

Conversely, for thin slices such as in bacon production, the feedtime required is short, so knife speed, and hence slicing rate, can be increased.

If desired, the image scanning array may be incorporated into the knife blade surface so that the face of the next slice is being scanned during the cutting of the current slice. Alternatively, since the surface of the current slice which was last in contact with the blade is the common surface of the current slice and the next slice, scanning that surface of the current slice using a static scanner may be performed instead of a dynamic scanner in the surface of the knife blade.

It has hitherto been stated that, for thin slices, slicing speed can be increased. At 'rasher' slicing speeds of 1000 per minute or more, the time available to complete an image scan and the associated computation on, say, the face of a side of bacon, is very short. However it is known that a simple two-dimensional scan is sufficient to produce a 'chop' (portion) well within the weight tolerances required by industry and legislation. The present invention is therefore based on the realisation that a pack of bacon rashers is sold on a value based upon the weight of the pack and not on the weight of the individual rashers. Equally, however, it is undesirable that a pack of bacon rashers should contain individual rashers of widely varying slice thickness.

Thus, in accordance with the invention, computer control as above-described may be applied to a rotary knife slicer to provide cutting control information which in the absence of other information will produce portioncontrolled bacon chops of correct weight by scanning the face of the side of bacon and estimating the slice thickness required for the bacon chop to have that particular weight, the computer, having determined the equivalent 'chop' thickness, being programmed to divide that thickness by the number of rashers required in the pack, so as to determine the mean rasher thickness, and to supplement the slice thickness cutting control information with fresh information derived from the mean rasher thickness information, to produce a pack of bacon rashers whose combined weight is equivalent to the said particular weight.

The invention also provides a method of slicing a body of product into slices in which the cutting rate and/or feed rate of the body of product are controlled by information derived from scanning the cut face of the body and/or the slices when removed therefrom, characterized in that the scanning is only performed once every N slicing operations and the data obtained is used to determine the slice thickness of the next N slices to produce an overall weight for the next given number of slices which lies within a given weight range.

The invention also lies in method of producing N slices from a body of a product, each slice having a substantially similar thickness to the other slices, and the N slices having an overall weight within a preselected range, the method comprising steps of: a) Scanning the end of a body (or a slice cut from the said end); b) Computing therefrom the area of the said end; c) Computing from the area value and the density of the product the thickness of a portion of the product required to produce an overall portion weight in said range; d) Computing the slice thickness needed to produce N slices which together make up the compound portion thickness; and e) Adjusting the feed and/or cutting rate of the body of product to obtain N slices of the product having the computed slice thickness.

Example of the invention If, for example, a pack weight of 150 gms is required, the slicing machine carries out a face scan to determine that an overall slice thickness of, say 20mm, is required.

However, the machine is programmed to produce 10 slices per pack, so that it then cuts a stack of 10 x 2mm slices instead of 1 x 20mm chop. The pack weight is then fed back to the computer of the slicer and used to produce the 'error' signal for correction of the control factor (density). This method means that, although the instantaneous scanning rate must be fast enough to accommodate a 1000-1200 slice/min production rate, the overall response rate of the control system can be reduced to the normal 'chop' production rate; making closed loop portion control of thin-sliced portions a practical proposition.

The system also offers considerable advantages over current techniques, which offer weight feedback control only, and which usually lead to bacon packs containing a very thin slice or a very thick slice as a 'make-weight' for the pack.

Effectively, therefore, the present invention proposes a system based on the concept of sub-dividing a 'chop' of controlled weight into an integral number of thinner slices to produce a 'rasher pack'. It is considered that such a system which effectively averages the pack weight over a pre-set number of slices, based upon an initial 'scan' of the raw material to estimate the overall pack thickness, offers considerable practical advantages over methods which attempt to image scan every rasher of bacon at the high rates already mentioned. Thus, central to the invention is the realisation that such scanning is not necessary, since a correct pack weight containing the requsite number of slices all of similar thickness is the main requirement and this can be obtained by sub-dividing the equivalent 'chop' determined by computerised control as described in the afore-mentioned patents.

Apparatus for putting the invention into effect is shown by way of example in the accompanying drawings in which: Figure 1 is a partial sectioned schematic side view of the apparatus, and Figure 2 is a diagramtic perspective view of the apparatus.

With reference to the drawings, the apparatus comprises feed means 1 for conveying a log of meat 2 to a blade 3, and a sensor 4 situated downstream of the blade 3.

Operation of the system is controlled by a computer control unit 5 into which instructions and data may be input by means of a keypad 6 connected to the control 5.

The feed means 1 comprises an end plate 7, which, in use, engages the end of the meat 2 to push the latter along a platform 8. The end plate 7 includes a lug 9 having a screw-threaded through - bore 10, via which the plate 7 is mounted on a screw-threaded shaft 11 situated beneath and to one side of the platform 8. One end of the shaft 11 is connected to a motor 12 which is operable to rotate the shaft about its elongate axis.

The motor 12 includes a servo unit (not shown) which is connected to the control unit 5 and which, in use, controls the operation of the motor 10 in response to signals from the control unit 5. The angular position of the shaft 11 is monitored by a position sensor (not shown) which is also included in the motor 12 and connected to the control unit 5.

In use, the motor 12 rotates the shaft 11, causing the lug 9, and hence the plate 7 to move the meat along the platform 8 towards the blade 3. As can be seen, the lug is so shaped as to avoid catching on the platform 8 as the plate 7 moves towards the blade 3. At any given time, a measure of the amount of movement of the plate 7 towards the blade 3 may be derived from the change of output of the sensor in the motor 12.

The end of the meat 2 opposite the plate 7 passes through an aperture 13 in a casing 14 which provides a housing for the blade.

The blade 3 includes a generally spiral cutting edge 15 and is, in use, rotated about a shaft 17 by a motor 18.

The operation of the motor 18 is controlled by means of a servo unit (not shown) connected to the control unit 5, and the rotational speed of the shaft 17 is monitored by a sensor (not shown) included in the motpr 18 and connected to the control unit 5.

The conveyer 19 is driven by a motor 21 having a servo unit (not shown) which is connected to the control unit 5 and is operable to control the motor 21. Information on the rate of travel of the belt of the conveyer 19, and thus of any product on the belt, is conveyed to the control unit 5 by a movement sensor (not shown) included in the motor 21.

The sensor 4 is also connected to the control unit 5, and is operable to scan the surface of a slice of meat passing thereunder, the scan direction being generally perpendicular to the direction of movement of the slice.

As the meat passes under the sensor 4, the latter performs a plurality of such scans, and for each scan generates a signal representative of the lateral extent of the meat along the line of that scan. From this signal, and the information obtained from the sensor in the motor 21, it is possible for the control unit 5 to derive a meausure of the area of the upper surface of the slice, and hence of the face of the meat 2 adjacent to the blade 3.

In operation, the keypad 6 is used to input into the control unit 5 the desired weight of each portion of meat to be removed from the meat 2, and the number of slices required for each portion. An estimate of the density of the meat 2 may also be input into the unit 5 via the keypad 6.

Using this information and the computed value of the area of the face of the log 2, the control unit 5 computes the desired portion and slice thickness for a given density of the meat 2.

The control unit 5 then controls the motor 12 to drive the shaft 11 so as to advance the meat 2 towards the blade 3 in a series of discrete steps, the distance of each of which corresponds to the computer thickness of each rasher. The control unit 5 also controls the blade 3 to rotate in the direction of the arrow A in such a way, that in the time between each sucessive step, the cutting edge 18 sweeps across the meat 2 to cut a slice therefrom.

Normally, the feed means 1 advances the log 2 at the same rate irespective of the desired thickness of each slice.

However, for very thin slices, the required rotational speed of the blade 3, for the given feed rate, may be too high. In such a case, the control unit 5 reduces the feed rate of the log 2 to allow a lower blade rotational speed to be employed: The slices produced by the blade 3 accumulate in a pile 22 which is then conveyed to the sensor 4 which scans the upper most surface of the top slice to provide a measure of the area of the face of the meat 2. This is then used in the calculation of the desired thickness of the next portion.

The apparatus includes a weighing station 30 situated downstream of the sensor 4. The weighing station 30 comprises a conveyer 31 similar to the conveyer 19, and a weighing cell 32 which is operable to generate a signal representative of the weight of a stack 33 of slices on the converyer 30.

In use, a stack of slices is conveyed from the sensor 4 to the weighing station 30, and the signal generated by the cell 32 is relayed to the control unit 5. The control unit 5 compares the measured and desired weights of the stack, and generates an error signal representative of any difference between the two values. The error signal may be used to adjust the density value used in the calculation of the thicknesses of subsequent portions.

Claims

1. In a meat cutting apparatus employing a knife slicer, for removing slices from the face of a body of meat ready for incorporation into sliced packs of predetermined weight, the surface area of the face of the body of meat is determined by the operation of scanning means, the thickness of a portion required to produce the predetermined weight is computed, the mean slice thickness required to produce a given number of slices from said portion is calculated, and the apparatus is operated to cut said number of slices of calculated mean thickness from the face of the body.

2. Apparatus according to claim 1 in which the pack weight incorporating said number of slices is compared with the required pack weight and an error signal fed back so that any weight error is corrected when the next predetermined number of slices are cut.

3. Apparatus according to either claim 1 or claim 2 in which the slicer is a rotary knife slicer of the kind in which, in use, a 'log' of product is fed laterally to a rotating knife mounted for rotation about a generally horizontal axis.

4. Apparatus according to claim 3 in which the knife is a spiral knife.

5. Apparatus according to claim 3 in which the knife is a hypocycloidal knife.

6. Apparatus according to any of the preceeding claims in which the scanning means comprises an image scanning array incorporated into the knife blade surface so that, in use, the face of the next slice is being scanned during the cutting of the current slice.

7. Apparatus according to any of claims 1 to 5 in which the scanning means comprises a scanner which is separate to the blade, and which scans the surface of the slice which was last in contact with the blade, that surface being the common surface of that slice and the next slice.

8. Apparatus substantially as described herein with reference to, and as illustrated in, the accompanying drawings.

9. A method of slicing a body of product into slices in which the cutting rate and/or feed rate of the body are controlled by information derived from scanning the face of the body and/or the slices when removed therefrom characterised in that the scanning is only performed once for any given number of slicing operations and the data obtained is used to determine the slice thickness for the next given number of slices to produce an overall weight for the next given number of slices which lies within a given weight range.

10. A method of producing N slices from a body of a product, each slice having a substantially similar thickness to the other slices, and the N slices having an overall weight within a preselected range, the method comprising steps of: a) Scanning the end of a body (or a slice cut from the said end); b) Computing therefrom the area of the said end; c) Computing from the area value and the density of the product the thickness of a portion of the product required to produce an overall portion weight in said range; d) Computing the slice thickness needed to produce N slices which together make up the compound portion thickness; and e) Adjusting the feed and/or cutting rate of the body of product to obtain N slices of the product having the computed slice thickness.

11. A method substantially described herein with reference to the accompanying drawings.