Radiant energy – Invisible radiant energy responsive electric signalling – With means to inspect passive solid objects
Patent
1990-03-21
1991-08-13
Fields, Carolyn E.
Radiant energy
Invisible radiant energy responsive electric signalling
With means to inspect passive solid objects
250560, 250349, 250341, 83 75, G01J 3312, G01J 2184
Patent
active
050398571
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention concerns scanners for sizing apparatus and in particular a radial scanner by which irregular shaped product can be measured for area sizing purposes before a portion is cut from the end which has been scanned.
BACKGROUND OF THE INVENTION
British Patent Specification No. 2149650 describes sizing apparatus in which the area of a piece of meat or like product which is to have pieces removed from the end face thereof by a band saw is measured by scanning linearly in a direction perpendicular to the direction of movement of the meat as it passes a scanning head.
The arrangement requires the meat to be supported in an unconventional manner and also requires the band saw to be operating in a vertical sense. Development of the machine has dictated that the meat should traverse with the cut face horizontal so as to be engaged by the horizontal section of a band saw and this requires that the end face of the meat shall be measured as it passes over a cutting table.
The development of the machine has also dictated that the meat is moved around a circular path in a magazine and the radius of the circular path is such that the meat cannot be considered to move in a straight line past a radial line of scanning windows.
It is therefore an object of the present invention to provide a scanner by which an accurate measurement of the area of the product can be obtained.
SUMMARY OF THE INVENTION
According to the present invention in apparatus for measuring the area of the end face of a piece of product which is to be cut by a band saw, and in which the product is supported on a horizontal surface of a cutting table as it is moved therearound in a generally circular path for engagement with the cutting edge of the saw blade, a line of inspection devices is arranged along a radius of the circular path in advance of the cutting position, and the line of inspection devices is addressed repetitively so as to produce electrical signals depending on whether product is positioned above the windows or not, and the electrical signals are combined in an electrical circuit and weighted by the circuit depending on the position of the detector along the radial line from which the signal is derived, greater weighting being given to signals arising from detectors located radially further from the centre of rotation than from detectors located nearer to the centre of rotation.
Typically the detectors are infra-red sensitive semiconductor junctions and each is associated with an infra-red source such as a light emitting diode which is arranged to direct infra-red radiation through a window at an angle of approximately 45.degree. to the phase of the window. If product exists on the other side of the window, some of the infra-red radiation is reflected by the surface of the product to pass once again through the window but this time at 90.degree. to the direction of the incident radiation and if a semiconductor detector junction is located at an appropriate position on the opposite side of the window, the reflected radiation will be received by the detector and thereby cause an increase in the current flowing therethrough.
The use of an infra-red radiation source and the use of infra-red sensitive detectors reduces the sensitivity of the device to changes in ambient lighting.
According to a preferred feature of the invention, the transmitters and detectors are located on opposite sides of each window below the opaque material surrounding each window and preferably cannot be viewed directly except at angles of very shallow incidence through the window. In this way incident infra-red and light radiation generally incident on the window will not penetrate and be seen by the detector.
By locating detectors and transmitters side by side so the windows can be positioned very close to one another and in a preferred arrangement, 32 pairs of transmitters and detectors are located along a line approximately 15 centimeters long.
In a preferred arrangement, the output current from each of the detectors is supplie
AEW Engineering Co. Limited
Dunn Drew A.
Fields Carolyn E.
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