Abstract: A metal detector used for identifying contaminants in packages on a conveyor. The detector includes coils a search head and an analog to digital converter generating a reactive signal and a resistive signal in response to the presence of a contaminant. During a learning mode a sample product passes through the metal detector providing a representative product effect signal which is stored by the reactive learn memory and the resistive learn memory. The learn memory values provide a reference value subtracted from each product signal during a normal production cycle, canceling the product effect caused by contaminants in individual packages. The product effect is monitored during successive cycles composed of a series of packages undergoing normal inspection by the metal detector. A tracking processor averages the product effect signal produced by the individual packages and continuously updates a product effect trend signal that is subtracted from each product signal.

Abstract: A metal detector (40) used for identifying contaminants in products (23) introduced into the metal detector by a conveyor. The detector (40) includes coils (1), a search head (2) and an analog to digital converter (3) that generates a reactive signal (13) in response to the presence of a contaminant in the region of the coils. A calculation processor (32) receives the reactive signal (13) along with the value of the conveyor speed (9) to determine a calibration ratio R that is unique to each individual metal detector (40). The optimum frequency F for metal detector operation is equal to the conveyor speed (9) divided by the ratio R. The ratio R simplifies the selection of filter parameters (4, 8) for a speed filter (30) which correlates the conveyor speed (9) with the frequency F so as to deliver an optimized signal to the detection algorithm (10) used to determine the presence of a contaminant based on the signal (13) derived from the coils (1).

Abstract: A first coil configuration (106) for use with a radio frequency metal detector includes a parallel wound oscillator coil (42) having two planar loops (43, 44). An oscillator excitation voltage (46) is applied simultaneously across both planar loops 43. The amount of induced voltage in two adjacent receiving loops (48, 49) is increased by closely spacing the oscillator coil loop (44) to one receiving loop (49) and by closely spacing the oscillator coil loop (43) to the other receiving loop (48). A second coil configuration (107) is a series aiding oscillator coil (55) having two planar loops (108, 54). The series aiding coil arrangement increases the oscillator current by decreasing the inductance of the oscillator coil (55) when a conductive contaminant (18) crosses the plane of the oscillator coil. The receiving or input coil (60) is formed of two separate loops (56, 57) wound in serial opposition to each other.

Abstract: A metal detector (40) used for identifying contaminants in packages (49, 50, 51) introduced into the metal detector by a conveyor. The detector (40) includes coils (1), a search head (2) and an analog to digital converter (3) that generates a reactive signal (13) and a resistive signal (14) in response to the presence of a contaminant in the region of the coils. A high pass filter (4) receives the reactive and resistive signals (13, 14). During a learning mode a sample product is introduced into the metal detector (40) to provide a representative product effect signal which is stored by the reactive learn memory (19) and the resistive learn memory (28). The learn memory values (29, 32) are forwarded to reference processors (20, 35) to provide a reference value which is subtracted from each product signal during a normal production cycle, thereby canceling the product effect caused by each individual package as it passes through the metal detector.

Abstract: A metal detector (40) used for identifying contaminants in products (23) introduced into the metal detector by a conveyor. The detector (40) includes coils (1), a search head (2) and an analog to digital converter (3) that generates a reactive signal (13) in response to the presence of a contaminant in the region of the coils. A calculation processor (32 ) receives the reactive signal (13) along with the value of the conveyor speed (9) to determine a calibration ratio R that is unique to each individual metal detector (40). The optimum frequency F for metal detector operation is equal to the conveyor speed (9) divided by the ratio R. The ratio R simplifies the selection of filter parameters (4, 8) for a speed filter (30) which correlates the conveyor speed (9) with the frequency F so as to deliver an optimized signal to the detection algorithm (10) used to determine the presence of a contaminant based on the signal (13) derived from the coils (1).

Abstract: A contaminant detection machine (1) including a conveyor (3) which causes an object under inspection (79) to pass through a plane (48) of emitted x-ray radiation. The plane is generated by an x-ray tube (55) that emits a lateral beam, thereby permitting the distance (88) between the x-ray tube and the object under inspection to be reduced. A photo diode arch mounting assembly (104) is placed above the object under inspection and is mated to a collimator assembly (125) that also serves as the mounting bracket for the x-ray generation assembly (38), thereby preserving optical alignment between the photo diode detector array (28) and the emitted x-ray plane (48). The detector array (28) scans the object under inspection (79) so as to produce a continuous series of discrete lines, each line being analyzed by an image processing unit (116) to determine the presence or absence of a contaminant.

Abstract: A contaminant detection machine (1) including a conveyor (3) which causes an object under inspection (79) to pass through a plane (48) of emitted x-ray radiation. The plane is generated by an x-ray tube (55) that emits a lateral beam, thereby permitting the distance (88) between the x-ray tube and the object under inspection to be reduced. A photo diode arch mounting assembly (104) is placed above the object under inspection and is mated to a collimator assembly (125) that also serves as the mounting bracket for the x-ray generation assembly (38), thereby preserving optical alignment between the photo diode detector array (28) and the emitted x-ray plane (48). The detector array (28) scans the object under inspection (79) so as to produce a continuous series of discrete lines, each line being analyzed by an image processing unit (116) to determine the presence or absence of a contaminant.