GB2179443A - Meat grader - Google Patents

Abstract

A meat grader comprises a probe 1 for insertion through a meat carcass to be graded. A light source 8 and a photosensor 9 are associated with the tip of the probe 1 whereby light from the light source reflected from the meat carcass is detected as the probe is inserted and/or retracted through the carcass. A first signal is generated representative of the amount of light detected by the light sensitive means. A second signal is generated designating memory locations representative of locations of the increments of axial movement of the probe through the carcass. The first signal is stored at addresses designated by the second signal. Various rates of change of the first signal with successive memory addresses are used to establish reference signal values, the addresses of which are subtracted to obtain fat and lean meat thicknesses. <IMAGE>

Description

SPECIFICATION Meat grader This invention relates to apparatus used to determine the thickness of meat and/or fat in a carcass, and is usefully employed as a pork grader.

Farmers are paid for their meat carcasses, often not only on the basis of total weight of the carcasses, but also on the absolute or relative amount of lean meat to fat in the carcass. In order to determine the absolute or relative thickness of lean meat and fat, a probe is pushed into the carcass, the probe carrying a light source and photosensor adjacent its tip for sensing whether the probe is passing through meat or fat. The amount of light reflected from the surrounding tissue from the light source, as sensed by the photosensor determines whether the sensor is embedded in lean meat or fat; fat reflects a large amount of light while lean meat reflects a small amount of light.

Such meat probes have been known and used for many years, for example as described and claimed in Canadian Patent 1,157,257 issued November 22nd, 1983 to Hennessy et al and Canadian Patent 1,075,457 issued April 15th, 1982 to Hennessy.

In both the aforenoted patents a probe carrying a light and photosensor as described above are pushed through the flesh of a carcass. As the probe moves through the carcass the position of the interfaces between highly and poorly reflective meat are noted. A mechanical plate supported at the surface of the carcass is linked to a position measuring apparatus, i.e. a distance scale. The distance that the probe moves between the aforenoted interfaces provides the operator an indication of the thickness of the meat and/or fat.

In Canadian Patent 1,075,457 a mechanical scale is controlled by the movement of the probe relative to the plate which rests on the surface of the carcass. The operator zeroes and notes the scale values. However in this apparatus we have determined that inaccuracies can occur dure to operator error in setting the scale and in reading the scale. The mechanical manner of linkage of the scale to the moving parts also can introduce errors due to wear of the apparatus.

In Canadian patent 1,157,257 signals represing the maximum amounts of light received by the light sensitive elements are stored in a pair of capacitors. These reflectance values are set when the probe is inserted into the carcass. The circuit automatically sets an intermediate level to establish the interface signal level between lean and fat meat. A second light source-light sensitive element pair are located adjacent a grid, which causes the light sensitive element to pulse as the grid passes between them when the meat probe is withdrawn. By counting the number of pulses between the selected intermediate voltage level and the ambient outside of the carcass, the depth of the outer fat level is determined. In the latter patent it is only possible to determine the outer fat thickness, and not the thickness of the lean meat.Further, the maximum and minimum signal values are stored on a pair of capacitors, which can leak and thus can give rise to erroneous readings.

Further, the intermediate voltage level is arbitrarily set, and due to the possible interleaving of fat and lean meat, it is possible to indicate an erroneous outer fat layer. In addition, the afforenoted patent measures the thickness by a direct physical determination by the position of the probe. Because the signal levels stored are analog in nature, they can drift, and can be rendered inaccurate.

The present invention, on the other hand, can determine the thickness of both the meat and fat layers (and/or their sum) with a high degree of accuracy. Signals corresponding to the reflected light values are stored in a digital memory. Rather than setting a value arbitrarily between the highest and lowest reflectance values, we have determined that a more accurate indication of the interface between fat and lean meat can be obtained by operating on the slope, that is the rate of change of the reflected light signal. The term "reflectance value" as used herein is intended to mean the light signal level received by the photosenor reflected by the carcass from the light source.

Rather than providing a mechanical distance measuring apparatus as in the Hennessy patents, the present invention does not concern itself with the absolute position of the probe or distance measuring mechanical parts, and thus does not measure the fat layer thickness directly from a base point as the probe is withdrawn as in Hennessy. The present invention requires only that there should be relative movement between the probe and an apparatus which moves as the probe is inserted and withdrawn from the carcass. This relative movement causes regular readings to be taken of the reflectance values at positions related to increments of movement, rather than at absolute positions. Thus there is no need to indicate a first signal reading position of the probe or mechanical distance measuring apparatus, with the attendant mechanical linkage errors, as in the aforenoted prior art patents.

Further, since all readings taken are digitally stored, they can be moved to archival memory for later recall in case of dispute between the farmer and marketing organization, the total or accumulative amounts of meat supplied by the farmer can be established and kept by the present apparatus, and the thickness values can be printed on a printer or transmitted to a digital computer.

In general, the invention is a meat grader comprising a probe for insertion through a meat carcass to be graded, a light source, and a light sensitive apparatus associated with the probe for detecting light from the light source reflected from the meat carcass as the probe is inserted and/or retracted through the carcass, apparatus for generating a first signal representative of the amount of light detected by the light sensitive means, apparatus for generating a second signal each predetermined increment of axial movement of the probe through the carcass, and apparatus for reading the first signal each time the second signal is generated, and for storing each read first signal.

A better understanding of this invention will be obtained by the detailed description below with reference to the following drawings, in which: Figure 1 is a perspective view of a meat probe, Figure 2 and 3 are a side sectional view and a top mechanical view illustrating details of the invention, Figure 4 is a block diagram of the electronic portion of the invention, and Figure 5 is a graph showing readings of reflectance values which are stored in the memory of the present invention.

Referring first to Fig. 1, a pointed probe 1 is fixed to and extends forwardly of a housing 2 to which a carrying handle 3 also is fixed.

An aiming plate 4 is fixed to the front of a pair of shafts 5 which extend through apertures 6 in the front wall of the housing 2. The probe 1 fixed to the housing extends through an aperture 7 in the aiming plate 4. A light source 8 and a photosensor 9 are embedded within the probe close to the tip, and are light-accessible at the surface thereof.

In operation, the probe tip is inserted into the carcass and is pushed through the meat and fat to the bone area. The aiming plate 4 rests at the surface of the carcass, causing shafts 5 to move through the apertures 6 in the housing 2. According to the prior art, the relative position of the aiming plate 4 to the probe was directly measured, in Canadian patent 1,075,457 for example by the use of a mechanical gauge, and in Canadian patent 1,157,257 by an electronic counter which begins incrementing and thus measuring the position at a predetermined signal level intermediate the highest and lowest signal levels detected on the photosensor. The thickness of the meat was determined by a count of pulses stored in the counter, each pulse being directly related to the position of the aiming plate relative to the probe.

In the present invention determination of the absolute position of the aiming plate relative to the probe is avoided, in order to reduce to eliminate the mechanical inaccuracy problems described earlier. The position of the aiming plate in the present invention merely causes readings of the signal value received from the photosensor to be taken and stored. Determination of the thickness of the lean meat and/or fat is determined in a microprocessor, operating on the stored signal values.

In the present invention a potentiometer is rotated by movement of the aiming plate; a DC current is applied to the potentiometer resulting in an analog output signal to be generated across the sliding tap and one terminal of the potentiometer in a well known manner.

This output signal is applied to an analog-todigital converter. The potentiometer's rotation is calibrated so that preferably 0.55 or 0.50 mm movement of the aiming plate causes a 1 bit change in the output signal from the analog-to-digital converter. The use of the above will be explained below, but first the mechanical structure to produce the above will be described with reference to Fig. 2 and 3.

Fig. 2 illustrates a vertical section through the housing showing the aiming plate, a shaft 5 and the apparatus important to illustrate the principles of the mechanical structure. Aiming plate 4 is shown coupled to shaft 5 which extends through aperture 6 in the front wall of housing 2. A potentiometer 10 has its rotational shaft axially coupled to a pulley 11 and is mounted in an axis orthogonal to the axis of shaft 5. A flexible strap 12 is fastened to the pulley at its end 13, the other end 14 of the strap being fixed to a cross brace 15 which is fixed to and couples both shafts 5.

Thus as aiming plate 4 is pushed toward the housing 2, shafts 5 extend further into the housing, pulling strap 12, and rotating pulley 11.

A bushing 16 extends axially from and is fixed to the pulley 11, and a second strap or wire 17 which is fixed to an extension spring 18 is wound in the opposite direction to strap 12 around bushing 16. The other end of spring 18 is fixed at a fixing point 19 to the housing. Thus as the pulley rotates as the aiming plate 14 extends into the housing, spring 18 is stretched, causing a counter restoring force against the direction of movement of aiming plate 14. Potentiometer 10 has its shaft coaxially fixed to bushing 16 and pulley 11, and is itself fixed to the housing 2.

Thus as aiming plate 4 is pushed into the housing, as pulley 11 rotates, the shaft of potentiometer 10 rotates.

Turning now to Fig. 4, a block schematic circuit of the invention is illustrated. Potentiometer 10 is shown as a block, but it will be understood that a constant current is applied to it, resulting in an output voltage dependent on the position of the rotor or shaft of the potentiometer. Also a light source 8 (preferably a light-emitting diode) has a constant current source 20 connected to cause it to illuminate in a well-known manner. A photosensor 9, preferably a phototransistor, receives the light from light source 8 reflected from the carcass, also in a well known manner.

The output of phototransistor 9 is connected to an analog-to-digital converter 21, which has its output connected to the data input of a memory 22. The output of potentiometer 10 is connected to analog-to-digital converter 23 which has its output connected to the input of an address selector 24. A microprocessor 25 is connected to the analogto-digital converters 21 and 23, to address selector 24 and to memory 22, in order to operate them in accordance with the algorithm to be described below.

Preferably a keyboard 26 and a display 27 are connected to microprocessor 25, the keyboard being used for inputting data such as farmer number, carcass unit number, etc. for storage in memory 22, and display 27 being used for communication with the operator, e.g. providing instantaneous readouts of the light reflectance signal, meat thickness, or other instructions, if desired, rather than merely storing them for later display or recording in other apparatus. Microprocessor 25 also has an input-output port shown as lead I/O, for providing an output signal of carcass number, and/or farmer number and lean meat/fat thicknesses to a storage computer, to a printer, or other peripheral apparatus.

As indicated earlier, the potentiometer's rotation is calibrated so that preferably 0.5 mm movement of the aiming plate causes a 1 bit change in the output of analog-to-digital converter 23. It has been found that a 2000 ohm potentiometer is suitable, and the analog-todigital converter should have a resolution selected to achieve the above. Microprocessor 25 monitors the output of analog-to-digital converter 23 and each time there is a 1 bit change in its output, due to rotation of the potentiometer 10, it enables the address selector 24 to read the output of the analog-todigital converter 23. The resulting address signal is then applied to the input of memory 22, which is also at that time enabled to read the output of analog-to-digital converter 21 by microprocessor 25.

The analog output signal of photosensor 9 is applied to analog-to-digital converter 21, which converts it to a digital signal. At the time of addressing memory 22 the microprocessor 25 also causes the analog-to-digital converter 21 (or a latch at its output) to output its signal as a data signal to the data inputs of memory 22. Memory 22 thus stores the digital signal level read at the address indicated by address selector 24.

In the above manner a complete sequence of readings will be obtained and stored in memory 22 as the probe is inserted and/or retracted from the carcass.

Fig. 5 illustrates a continuous graph of signal value stored at each memory location. The graph consists of a series of stepped amplitude levels, each step corresponding to a specific reading. Thus the axis "successive readings" corresponds directly to memory locations, while the signal value amplitude represents the digital value of the stored signal at each memory location resulting from the photosensor.

Looking from left to right, it may be seen that a very low signal level, representing very low reflectance (the probe being external to the carcass) it first stored at low addresses, followed by high readings which represent the outer layer of fat. Once the probe has entered a lean meat region, the signal level drops to a low level extending over a range indicated by L. The reflectance then increases again as the photosensor reaches the bone and sinew region where there are additional regions of fat.

It is desired to determine various signal level reference points in order to determine where the meat and/or fat and/or ambient interfaces occur.

A first reference point (value and address) determines the sensed light value when the photosensor enters or leaves the carcass outer fat layer. This reference point "o" can be determined by several possible means, the preferred one of which is to determine the interface between the very low light value and a high increase rate of change of light (i.e. a high slope). Alternatively an absolute low light value can be used.

In order to determine a second reference point, first a point "a" is determined when the light value has decreased by a value of 60 or more units over a distance of 3 mm from a peak following the point "0". The microprocessor then searches for a point "b" where the light value is increasing or has been constant for three successive readings. This point "b" is interpreted as the light value for the lean meat (low reflection).

A point "c" is then determined which is the largest light value between "a" and preferably six readings prior to a The second reference point (ref 2nd) is established where the middle light value between points "b" and "c" crosses the curve (which will often be close to point "a"). This establishes the fat to lean meat interface.

A third reference point is established where the same light value as at the second reference point crosses the curve a second time, i.e. at "d". If no point is found, the light value of the second reference point is reduced by an arbitrary value e.g. 10 is used. This sequence should continue until the third reference point is found.

Thus it may be seen that the light signal levels between the first and second reference points are due to the outer layer of fat, and the light signal levels between the second and third reference points are due to the lean meat. The light signal levels between the first and third reference points are caused by the combined thickness of fat and lean meat.

Subtracting the addresses between the reference points, and multiplying the differences by a constant thus provides an indication of the fat, lean meat and total thicknesses.

These signals can be stored in the memory for later retrieval, successive totals can be added, the values can be output via the I/O port to a printer or computer, etc. It should be understood that successive increasing memory addresses is intended to mean increasing in either the positive or negative direction.

The structure described above clearly has significant advantages over the prior art both in manipulation and storage of data, and in the accuracy of thickness measurement, and also since a direct reading of thickness does not depend on a measurement of absolute aiming plate position.

A person understanding this invention may now conceive of alternative variations based on the principles described herein. All are considered to be within the sphere and scope of this invention as defined in the claims appended hereto.

Claims (12)

1. A meat grader comprising: (a) a probe for insertion through a meat carcass to be graded, (b) a light source, and a light sensitive means associated with the probe for detecting light from the light source reflected from the light source reflected from the meat carcass as the probe is inserted and/or retracted through the carcass, (c) means for generating a first signal representative of the amount of light detected by the light sensitive means, (d) means for generating a second signal each predetermined increment of axial movement of the probe through the carcass, (e) means for reading the first signal each time the second signal is generated, and for storing, each read signal in a memory at addresses corresponding to the second signals.

2. A meat grader as defined in claim 1 including means for determining the thickness of lean meat represented by a stored low light reflection value and/or the thickness of fat meat represented by a stored high light reflection value comprising means for establishing the addresses of stored signals representing the interfaces between low and light values, means for determining the number of first sig nals stored between the addresses, and means for multiplying the number of first signals stored between the addresses by a predetermined constant to provide lean and/or fat meat thickness representation signals for storage and/or display.

3. A meat grader as defined in claim 1 further comprising means for reading the stored first signals, and for (i) determining a high positive rate of change in stored values at successive addresses, and for establishing a first reference signal value at an address location having a low signal level just prior to the addresses having said high rate of change values, (ii) determining a second reference signal value at an address having a value related to a predetermined minimum negative rate of change in said values with increasing addresses, (iii) determining a third reference signal value at the first address higher than that of the second reference point following a range of increasing values with increasing addresses, which contains a value equivalent to that at the second reference point, or a value a predetermined amount less than the value equivalent to the second reference point, whichever is the greater, means for subtracting the addresses of the first and second reference points and multiplying the difference by a constant to obtain a signal representative of the fat content of a carcass, and for subtracting the addresses of the second and third reference points and multiplying the difference by a constant to obtain a signal representative of the lean meat content of a carcass, and means for providing said representative signals for display or storage.

4. A meat grader as defined in claim 1 further comprising means for reading the stored first signals, and for (i) determining a high positive rate of change in stored values at successive addresses, and for establishing a first reference signal value at an address location having a low signal level just prior to the addresses having said high rate of change values, (ii) determining a first marker value "a" at an address location higher than said first reference value where the rate of change of stored values has decreased by a predetermined amount over a predetermined number of values having increasing addresses, determining a second marker value "b" at an address higher than the address of the first marker value where the value is increasing or has remained constant over a predetermined number of increasing addresses, determining a third marker value "c" at the address containing the largest value between the first marker value and a value at an address a predermined number of addresses preceding, and establishing a second reference signal value at the address midway between the addresses containing the second and third marker values, (iii) establishing a third reference signal value at the first address higher than that of the second marker value which contains a value equivalent to that at the second reference point or a value a predetermined amount less than the value equivalent to the second reference point, whichever is the greater, and means for transmitting said first, second and third reference signals via a communication line to a printer or a remote terminal.

5. A meat grader as defined in Claim 1 further comprising means for reading the stored first signals, and for (i) determining a high rate of change in stored values at successive addresses, and for establishing a first reference signal value at an address location having a low signal level just prior to the addresses having said high rate of change values, (ii) determining a first marker value "a" at an address location higher than said first reference value where the rate of change of stored values has decreased by a predetermined amount over a predetermined number of values having increasing addresses, determining a second marker value "b" at an address higher than the address of the first marker value where the value is increasing or has remained constant over a predetermined number of increasing addresses, determining a third marker value "c" at an address containing the largest value between the first marker value and a value at an address a predetermined number of addresses preceding, and establishing a second reference signal value at the address midway between the addresses containing the second and third marker values, (iii) establishing a third reference signal value at the first address higher than that of the second marker value which contains a value equivalent to that at the second reference point or a value a predetermined amount less than a value equivalent to the second references signal value, whichever is the greater, means for subtracting the addresses of the first and second reference signal values and multiplying the difference by a constant to obtain a signal representative of the fat content of a carcass, and for subtracting the addresses of the second and third reference signal values and multiplying the difference by a constant to obtain a signal representative of the lean meat content of a carcass, and means for providing said representative signals for display or storage.

6. A meat grader as defined in claim 5 further including means for transmitting said representative signals to a printer or a remote terminal.

7. A meat grader as defined in claim 5 including a light-emitting diode light source connected to the input of a first analog to digital converter, the output of the converter being connected to the data input of a digital memory, a photosensor connected to the input of a second analog to digital converter, the output of the second converter being connected to the input of an address selector, the output of the address selector being connected to the address input of the memory, a microprocessor connected to the address selector, the memory and the analog to digital converters for enabling the converters, and for controlling the address selector and memory, whereby said first signals are stored at addresses represented by the second signals, and whereby said first signals can be read by the microprocessor at said addresses, and said representative signals generated therein.

8. A meat grader as defined in claim 1 including a light-emitting diode light source connected to the input of a first analog to digital converter, the output of the converter being connected to the data input of a digital memory, a photosensor connected to the input of a second analog to digital converter, the output of the second converter being connected to the input of an address selector, the output of the address selector being connected to the address input of the memory, a microprocessor connected to the address selector, the memory and the analog to digital converters for enabling the converters, and for controlling the address selector and memory, whereby said signals are stored at addresses represented by the second signals.

9. A method of grading a carcass comprising: (a) obtaining the light reflectivitiy of the meat in a carcass at progressive depths within the meat, (b) storing digital signals representative of said reflectivity at successive memory addresses representative of a relative location of the particular reflectivity from an indeterminate position outside the meat to an indeterminate depth within the meat, (c) (i) determining a high rate of change in stored values at successive addresses, and establishing a first reference signal value at an address having a low signal level just prior to the addresses having said high rate of change values, (ii) determining a second reference signal value at an address storing a value related to a predetermined minimum negative rate of change in said values with increasing addresses, (iii) determining a third reference signal value at the first address higher than that of the second reference signal value following a range of increasing values with increasing addresses, which contains a value equivalent to that at the second reference points, or a value a predetermined amount less than the value equivalent to the second reference point, whichever is the greater, and means for subtracting the addresses of the first and second reference point and multiplying the difference by a constant to obtain a signal representative of the fat content of a carcass, and for subtracting the second and third addresses and multiplying the difference by a constant to obtain a signal representative of the lean meat content of a carcass, and means for providing said representative signals for display or storage.

10. A method as defined in claim 9, including: determining a first marker value "a" at an address location higher than said first reference value where the fate of change of stored values has decreased by a predetermined amount over a predetermined number of values having increasing addresses, determining a second marker value "b" at an address higher than the address of the first marker value where the value is increasing or has remained constant over a predetermined number of increasing addresses, determining a third marker value "c" at the address containing the largest value between the first marker value and the value at an address a predetermined number of addresses preceding, and establishing the second reference signal value at the address midway between the addresses containing the second and third marker values, and establishing the third reference signal value at the first address higher than that of the second marker value which contains a value equivalent to that at the second reference point or a value a predetermined amount less than the value equivalent to the second reference point, whichever is the greater.

11. A meat grader substantially as herein described with reference to and as shown in the accompanying drawings.

12. A method of grading a carcass substantially as herein described with reference to and as shown in the accompanying drawings.