GB2377362A

GB2377362A - Non-stop slicing machine controlled by upstream sensor

Info

Publication number: GB2377362A
Application number: GB0215333A
Authority: GB
Inventors: Richard Edward Sawford
Original assignee: AEW Engineering Co Ltd
Current assignee: AEW Engineering Co Ltd
Priority date: 2001-07-13
Filing date: 2002-07-03
Publication date: 2003-01-15
Anticipated expiration: 2022-07-03
Also published as: GB0215333D0; GB2377362B; GB0117101D0

Abstract

A high speed slicing machine, especially for slicing joints of varying cross-sectional area, wherein the product is viewed in a detection plane (48) a distance (x) ahead of the plane of a rotary knife (28) to determine its cross-sectional profile, and conveying means (24, 26) transports the joint through the plane of the rotary knife to cut the joint into slices or portions, at a distance (x) + (y) downstream of the detection plane, where (y) is the thickness required for a slice or portion in order to produce slices or portions of equal volume or weight without stopping the conveyor or the knife during cutting operations.

Description

Title: Slicing Machine Field of the Invention This invention relates to a slicing machine, especially but not exclusively for slicing joints of meat from a product log of irregular and varying cross-sectional area.

Background to the invention Slicing machines are known which include a camera means for viewing the periphery of the leading face of a product log of varying cross-sectional area, computing the instantaneous cross-sectional area and adjusting the lengths of product cut from the product log in order to obtain joints of approximately the same weight. Typically in such a machine using a rotary knife, a control system stops rotation of the knife in between slicing operations, the product log is advanced through a selected distance dependently on the cross-sectional area of its leading face measured during the immediately preceding cutting operation, and the conveyor is stopped following its selected distance advance while the next cutting operation takes place. Inertia involved in starting and stopping the conveyor means and the rotary knife slows down the overall speed of operation of the machine. Requirements for adequate computing times also slow down the overall speed of operation of the machine.

Summary of the Invention According to one aspect of the invention, there is provided a slicing machine wherein a conveyor means advances a product to be sliced towards and past a rotary cutting knife, the machine including a vision system having a camera means viewing the product on the conveyor means at a predetermined distance (x) ahead of the plane of the rotary knife, and

a computerised control system receiving signals from the camera means and producing interlocked control signals for respective drive motors for the conveyor means and the rotary knife whereby, without stopping either the conveyor means or the rotary knife, the product is cut when its leading face is at a distance (x) + (y) ahead of the vision system, where (y) is a distance corresponding to a required thickness for a slice.

With the machine in accordance with the invention, loss of machine speed due to inertia is minimised, while the distance (x) can be made sufficiently large to avoid problems with computation times.

Although in accordance with this aspect of the invention the conveyor and the knife are continuously in motion, in one embodiment the conveyor is driven at a constant speed throughout but the speed of rotation of the knife is slowed between cutting operations. The dwell period for which the knife is slowed is programmable, and varied to produce different lengths of product. Then once the profile of the product log has been calculated the critical speeds are mapped to a position on the conveyor means, thus continuously locking together the relative motions of the conveyor and the knife. In general, if a shorter dwell period is called for, the speed of rotation of the knife will be reduced to a lesser extent than when a longer dwell period is called for.

Preferably, the conveyor means comprises an infeed conveyor and a mainfeed conveyor which transports the product log past the rotary knife. The two conveyors are preferably electronically geared together to run in synchronism at equal speeds. The product can conveniently be illuminated in the product detection plane, which passes between and is normal to the axes of the conveyors. In the case of a product with non-varying crosssectional profile, the distance (x) may conveniently be greater than the distance between the profile measurement plane and the plane of rotation of the knife. The camera means views the product in the plane of illumination to determine its instantaneous peripheral profile in that plane, enabling a cross-sectional area times distance calculation to be carried out by the computerised control means in order to determine a product volume profile,

thus determining the length (y) required to be cut from the product log, when the product log has been advanced by the distance (x) + (y).

The control means preferably develops trigger pulses to fire the camera means at programmable intervals, enabling volume calculations to be made independently of conveyor speed.

The rotary knife may be slowed between the actual cutting operation. In a modification, because the portion volume measurement is independent of speed if the conveyor position is employed to trigger cutting operations, the conveyor means can be programmed to change to a lower speed just before a cutting operation and be accelerated again afterwards, thus giving a better cut profile at higher operating speeds. This alternative embodiment is especially suitable for cutting relatively larger joints of the product.

A preferred control system comprises a main controller and a four axis position controller receiving signals from the main controller, the position controller sending drive signals, typically via amplifiers, to the infeed conveyor motor, the mainfeed conveyor motor, the rotary knife motor and an outfeed conveyor motor. Preferably, each drive motor provides a position and speed feedback signal to the four axis position controller, so that effectively each motor is servo controlled.

According to another aspect of the invention, there is provided a method of controlling a slicing machine of the kind wherein a conveyor means advances a product to be sliced towards and past a rotary cutting knife, wherein the product on the conveyor means is viewed by a vision system at a predetermined distance (x) ahead of the plane of the rotary knife, vision signals are processed to produce interlocked control signals which control drive motors for the conveyor means and the knife, and without stopping either the conveyor or the knife, the product is cut when its leading edge is a distance (x) + (y) ahead of the vision system, where (y) is a distance corresponding to the required thickness for a slice.

Description of Embodiment An exemplary slicing machine in accordance with the invention is now described with reference to the accompanying drawings, in which :- Fig 1 is a block schematic diagram of the overall control system for the slicing machine; Figs 2 and 3 are explanatory diagrams illustrating the overall control system logic, Fig 3 also showing the layout of the conveyors and rotary blade in the machine; Figs 4 and 5 are diagrams relating to the options of slowing the knife and/or the conveyors during the cutting; and Fig 6 shows part of the machine with the vision inspection means superimposed.

Referring to Fig 1, the overall control system for the slicing machine comprises a 4-axis position controller 10 receiving position control signals from a computerised main control system 12. The position controller 10 generates drive signals fed to drive motors 14,16, 18,20 via power amplifiers 22A, B, C, D. The drive motors consist of an infeed conveyor motor 14 driving an infeed conveyor 24 through a gearbox 24A, a main feed conveyor motor 16 driving a main feed conveyor 26 via a gearbox 26A, a knife blade motor 18 driving a rotary knife 28 via a gearbox 28A and an outfeed conveyor motor 20 driving an outfeed conveyor 30. The drive motors provide feedback signals 27 to the 4-axis position controller 10, thus effectively creating a 4-axis servo drive system. The rotary knife28 operates at a small gap between the main feed conveyor 16 and the outfeed conveyor 20.

The main control system 12 is programmable from a keypad 32 which includes a menu and control display 32A. The control system 12 has a digital system input and output 34,34A and, more importantly, is in two way communication with a vision control system 36 for

three cameras 38,40, 42, which view a product being conveyed by the conveyors 24,26 towards the rotary knife 28. The vision control system also projects a view of the product as seen by the cameras on a display unit 46. The vision control system 36 is supervised by the main control system 12 and sends information about the product to the main control system, which after making calculations about the product based on the information received, generates the position control signals for the 4-axis drive system.

The logic by which the control system of Fig 1 operates will now be explained, making reference to Figs 2 and 3.

Referring first to Fig 2, by entering into the keypad 32 a required weight of a slice or portion and an assumed or known mean density of the product, the computer in the main control system 12 can calculate a required volume for a slice or portion of product to be cut. This calculated volume is entered into the main control system 12. If, as also shown for convenience in Fig 2, the product density cannot be assumed, the product can be weighed by a weighscale 47, whereby after scanning a volume profile can be built up from cross-sectional measurements of the product taken a programmable distance (y) apart, thus enabling the density of the product to be calculated, whereby to enable the required volume of a slice or portion to be determined. From the required volume figure, when the product has been scanned by the cameras 38,40, 42, so that its peripheral shape and a volume profile is known, the main control system 12 is able to determine the required length or thickness (y) of product required to cut slices or portions of required equal volume. Referring to Fig 3, the infeed and main conveyors 24,26 are electronically geared together to run at equal speeds, and the plane 48 (illuminated by lasers 50,52, 54,56) normal to the direction of conveyance in which the cameras 38,40, 42 detect the product is a distance having a fixed relationship to a distance (x) upstream of the rotary knife 28. Thus, the knife repeatedly operates to cut the product at a distance (x) + (y) downstream of the viewing cameras, at intervals corresponding to the time taken for the conveyors to move the product through the distance (y). The fact that the inspection plane 48 is a predetermined distance related to the distance (x), upstream of the rotary knife 28, enables

the computerised control system readily to calculate the distance (y), which can vary with the determined product profile, without stopping the movement of the conveyors, thus increasing overall machine slicing speed.

However, it is generally necessary either to slow the speed of rotation of the knife between cuts or to slow the speed of the conveyors during cuts. In this connection, it is to be noted that the detection cameras are fired by electronically developed pulses, at programmable conveyor movement distances. This makes the subsequent volume calculation, and thus the distance (y), independent of the speed of the conveyor. When the product profile has been calculated, the initial relative speeds of movement of the conveyors and the rotary knife are mapped to a position on the main conveyor, thus continuously locking together the operations of the conveyors and knife. This makes it possible, as shown in Fig 4, either to step the speed of rotation of the knife, without actually stopping it, to match different required cut lengths (y) for a given conveyor speed, or alternatively, as shown in Fig 5, to slow the speed of the conveyors while, and only while, cutting is taking place. A combination of both slowing operations is also possible. In the case of slowing the conveyors, the infeed and main conveyors can be pre-programmed to change to a lower speed just before a cut and accelerate afterwards, whereby to give better cut product profiles at higher cutting speeds, especially for longer joints.

Fig 4 shows the blade cut speed profile 58 when the speed of the conveyor is kept constant through cutting, while Fig 5 shows the blade cut speed profile 60 and the conveyor speed profile 62 when the conveyors are slowed during cutting. Variations of speed of the blade and/or conveyors during cutting are programmable.

The 4-axis position controller 10 shown in Fig 1 is therefore important, because, as previously stated, critical speeds of operation are mapped to a position on the main conveyor, and therefore the rotary knife is operated at times related to the conveyor position. This relationship is determined by the position control signals fed to the 4-axis position controller 10, which in turn generates the drive signals for the motors driving the conveyors and the knife. Because volume measurement is independent of conveyor speed,

the latter can be pre-programmed to change to a lower speed just before cutting and accelerate just afterwards.

The foregoing description relates primarily to the control system for the slicing machine.

Part of the machine to which this control system is applied is shown in Fig 6 with the vision system superimposed. Visible in the diagram are the three cameras 38,40, 42 which operate to view the product in the detection plane 48, which is located in the small gap between the infeed conveyor 24 and the main conveyor 26. The length of the main conveyor 26 thus substantially corresponds to a fixed distance equal to the distance (x).

The laser lights 50,52, 54,56 illuminate the product around a line in the detection plane, and cameras 38,40, 42 view the product in this plane along inclined axes. The drawing makes clear the exact positions of the laser lights and cameras which are effective in the detection plane 48.

It will be noted that operations take place within an enclosed environment established by a housing 66 through which the product is conveyed. An extraction fan 68 keeps the environment cool and dry.

Claims

Claims 1. A slicing machine wherein a conveyor means advances a product to be sliced towards and past a rotary cutting knife, the machine including a vision system having a camera means viewing the product on the conveyor means at a predetermined distance (x) ahead of the plane of the rotary knife, and a computerised control system receiving signals from the camera means and producing interlocked control signals for respective drive motors for the conveyor means and the rotary knife whereby, without stopping either the conveyor means or the rotary knife, the product is cut when its leading face is at a distance (x) + (y) ahead of the vision system, where (y) is a distance corresponding to a required thickness for a slice.
2. A slicing machine as claimed in claim 1 wherein the distance (x) is made sufficiently large to allow for computation times.
3. A slicing machine as claimed in claim 1 or 2 wherein the conveyor is driven at a constant speed throughout but the speed of rotation of the knife is slowed between cutting operations.
4. A slicing machine as claimed in claim 3 wherein the dwell period for which the knife is slowed is programmable.
5. A slicing machine as claimed in claim 3 or 4 wherein the dwell period for which the knife is slowed is varied to produce different lengths of product.
6. A slicing machine as claimed in any of claims 1 to 5 wherein the profile of a product log is calculated and the critical speeds are mapped to positions on the conveyor means, thus continuously locking together the relative motions of the conveyor and the knife,

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whereby, if a shorter dwell period is called for, the speed of rotation of the knife will be reduced to a lesser extent than when a longer dwell period is called for.
7. A slicing machine as claimed in any of claims 1 to 6 wherein the conveyor means comprises an infeed conveyor and a mainfeed conveyor which transports the product log past the rotary knife.
8. A slicing machine as claimed in claim 7 wherein the two conveyors are electronically geared together to run in synchronism at equal speeds.
9. A slicing machine as claimed in any of claims 1 to 8 wherein the product is illuminated in the product detection plane, which passes between and is normal to the axes of the conveyors.
10. A slicing machine as claimed in claim 9 wherein the distance (x) is greater than the distance between the profile measurement plane and the plane of rotation of the knife.
11. A slicing machine as claimed in claim 10 wherein the camera means views the product in the plane of illumination to determine its instantaneous peripheral profile in that plane, enabling a cross-sectional area times distance calculation to be carried out by the computerised control means in order to determine a product volume profile, thus determining the length (y) required to be cut from the product log, and determining the distance (x) + (y) through which the product log is to be advanced.
12. A slicing machine as claimed in any of claims 1 to 11 wherein the control means develops trigger pulses to fire the camera means at programmable intervals, enabling volume calculations to be made independently of conveyor speed.
13. A slicing machine as claimed in claim 12 wherein the conveyor position is employed to trigger cutting operations and the conveyor means is programmed to change to a lower

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speed just before a cutting operation and be accelerated again afterwards, thus giving a better cut profile at higher operating speeds.
14. A control system for a slicing machine as claimed in any of claims 7 to 13 comprising a main controller and a four axis position controller receiving signals from the main controller, the position controller sending drive signals to an infeed conveyor drive motor, a mainfeed conveyor drive motor, a rotary knife drive motor and an outfeed conveyor drive motor.
15. A control system as claimed in claim 14 wherein each drive motor provides a position and speed feedback signal to the four axis position controller, so that effectively each motor is servo controlled.
16. A method of controlling a slicing machine of the kind wherein a conveyor means advances a product to be sliced towards and past a rotary cutting knife, wherein the product on the conveyor means is viewed by a vision system at a predetermined distance (x) ahead of the plane of the rotary knife, vision signals are processed to produce interlocked control signals which control drive motors for the conveyor means and the knife, and without stopping either the conveyor or the knife, the product is cut when its leading edge is a distance (x) + (y) ahead of the vision system, where (y) is a distance corresponding to the required thickness for a slice.
17. Apparatus and methods of controlling same to slice a log of product into portions, substantially as herein described and with reference to the accompanying drawings.