Electronic Product-sizing Apparatus

Abstract

Articles such as crops are sized while being moved past a photoelectric sizing station by a continuously moving conveyor. A set of spaced sizing cells at the sizing station gauge the dimensions of the article to emit a signal if the size and shape of the article is within a predetermined and adjustable range. Generation of the signal operates an ejection device to remove the article from the conveyor.

Description

This invention relates to a photoelectric sizing device particularly useful for products such as potatoes, cucumbers, etc.

Dimensional sizing apparatus of the photoelectric type arranged to gauge the size and shape of an object as it is carried past a sizing station, is well known. However, the need exists for a relatively simple photoelectric sizing apparatus capable of being adjusted for different products, conveyor speeds and in accordance with different sizing tolerances.

In accordance with the present invention, the size and shape of products continuously conveyed past a sizing station are gauged by sizing cells and a source of light projecting a shadow onto a surface mounting the faces of the sizing cells. A set of inside "accept" cells when covered by the shadow of a product at the sizing station during an operational interval, causes generation of an accept signal if any one of a corresponding set of outside "reject" cells are not covered by the shadow during the same interval of time. The outside set of reject cells may be adjusted relative to the inside set of cells in accordance with a desired sizing tolerance. Through adjustable time delaying devices, the signal generating circuit associated with the sizing cells may accommodate different product size ranges and conveyor speeds. The signal generated when an article of predetermined size and shape is gauged, operates an ejection device to remove the product from the conveyor.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIG. 1 is a schematic front elevational view of the product sizing arrangement associated with the present invention.

FIG. 2 is a top plan view of the arrangement shown in FIG. 1.

FIG. 3 is an electrical circuit diagram associated with the product sizing apparatus of the present invention.

FIG. 4 is a graphical diagram illustrating the operational sequence associated with the product sizing apparatus.

Referring now to the drawings in detail, FIG. 1 illustrates a continuously moving conveyor 10 adapted to carry products or articles such as potatoes 12 past one or more sizing stations located in close laterally spaced relation to the conveyor. A sizing head 14 is associated with each sizing station which also has associated therewith a source of radiation such as a tungsten filament lamp 16 disposed on one lateral side of the conveyor opposite the side of the conveyor on which the sizing head 14 is located. The light from the lamp 16 impinges on the sensing surface 18 of the sizing head which is disposed in a plane parallel to the direction of travel of the conveyor.

It will be apparent from FIGS. 1 and 2, that when a product 12 is at the sizing station, the lamp 16 will project a shadow of the product onto the sizing surface 18. The sizing head mounts a plurality of photoelectric sizing cells, the sensing faces of which are disposed in the plane of the surface 18. The sizing cells include a set of inside accept cells consisting of horizontally spaced cells 20 and 22 for gauging a length dimension parallel to the direction of travel of the conveyor and a cell 24 vertically spaced above the conveyor to gauge the height dimension of the product. If the product is within a predetermined size and shape, the inside cells 20, 22 and 24 will during a short interval of time be covered by the shadow of the product or disposed within its shadow outline 26 as shown in FIG. 1. Also, during the same interval of time the shadow of the product of predetermined size and shape does not cover any one of a set of outside reject cells 28, 30 and 32 adjustably positioned relative to corresponding accept cells 20, 22 and 24.

By adjusting the position of the outside reject cells, different sizing tolerances may be accommodated. Also, the spacing between the inside cells may be varied together with the outside reject cells in the respective sizing heads, if more than one is utilized, in order to remove products within different size ranges at each of the sizing stations. The products are removed from the conveyor by any suitable ejection device having an electromagnetically operated solenoid element 34 as shown in FIG. 3. The ejector solenoid 34 forms part of a control circuit housed within each of the sizing heads. By means of the circuit, a signal is generated to pulse the solenoid 34 whenever the shadow of a product at the sizing station covers the inside set of the cells 20, 22 and 24 but does not cover the outside set of reject cells 28, 30 and 32. Dependent upon the size and shape of the product and the speed of the conveyor, the inside set of cells will be covered by the shadow of the product at the sizing station for a predetermined exposure period 36 as graphically depicted in FIG. 4. After a first time delay period 42, a pulse 38 is generated having a predetermined pulse duration 40 terminating after the elapse of the exposure period 36. A second pulse 44 is generated at the end of a second time delay period at which time the pulse 38 is terminated and an ejection pulse 46 initiated. An operational cycle is completed at the end of the ejection pulse 46 automatically resetting the circuit for another operational sequence. It will therefore be apparent, that the ejector solenoid 34 is pulsed after the product is sized as reflected by a signal pulse 38 of a sufficiently long duration to ensure proper spacing between cycles in order to avoid interference.

The circuit shown in FIG. 3, includes a DC source of voltage 48 varying within plus or minus 1 percent from a 21.5 VDC value. The positive terminal of the source 48 is connected by a fuse 50 to the contact 52 of a double pole, single throw power switch 54 having a second contact 56 connected by fuse 58 to an AC source of voltage at 60. While the AC source of voltage 60 furnishes the power for the ejector solenoid 34, the DC source of voltage 48 supplies control voltage for generating a signal pulse under control of the photoresponsive sizing cells as aforementioned.

The negative terminal of the DC voltage source 48 is connected through a current-limiting resistor 62 to one terminal of each of the cells 20, 22 and 24 and to the "off" contact 64 of a mode selector switch 66, having an "on" contact 68 engaged with the switch in the position illustrated in FIG. 3. In the "on" position illustrated, the mode selector switch 66 connects the cell 24 to the control electrode or base of an NPN-type transistor 70. The switch 66 in the "on" position connects cells 22 and 24 to the base of transistor 70 and is shunted by a load resistor 72 connected to the base. Connector assembly 74 connects the cell 22 to the switch 66 and also directly connects the cell 20 to the base bypassing the switch. Thus all three cells 20, 22 and 24 are connected in parallel to the base. When the mode selector switch 66 is in the "off" position engaging contact 64, the negative terminal of the DC source 48 is connected in series with the current-limiting resistor 62 and the photocells 22 and 24 to the base of the transistor shunted by the photocell 20. The "off" position of the switch 66 is utilized in order to regulate the circuit as will be explained hereafter.

The inside photocells 20, 22 and 24 control the negative reverse bias applied by the DC source 48 to the base of transistor 70 to normally prevent current flow between the emitter and collector connected in series with the outside reject photocells 28, 30 and 32. The series connected reject cells are connected to a source of positive potential from which a forward bias is applied to the base through adjustable resistor 76 in series with a current-limiting resistor 78. The forward bias is supplied from the positive terminal of DC source 48 through power switch 54 and relay switch 80. When reverse bias is removed from the base, transistor 70 is rendered conductive to conduct current and complete a relay energizing circuit for the relay coil 86 thereby energized to close the normally open relay switch 82.

In the normal position of the relay switch 80, the positive terminal of the DC power source is connected through the series connected cells 28, 30 and 32, the transistor 70 and resistor 84 to one terminal of the relay coil 86, the other terminal being connected to the negative terminal of the power source. When the photocells 28, 30 and 32 are exposed to light from the lamp 16 so as to maintain a low resistance value, and reverse bias is removed from the base of the transistor 70 by an increase in the resistance values of the photocells 20, 22 and 24, an energizing current pulse will be conducted through the relay coil 86 to close the normally opened relay switch 82. The terminals of the relay coil 86 are, however, shunted by a time delay capacitor 88 in parallel with resistor 90 and adjustable resistor 92. Resistor 92 is adjustable to vary the duration of the first time delay 42 before the current conducted by transistor 70 causes energization of the relay coil 86. Thus, the duration of the current pulse or conductive period of transistor 70 must exceed the first time delay period 42. The speed of the products, their sizes and irregular shapes, causes the pulse to vary in strength and duration. The minimum pulse strength for energizing relay coil 86 is established by the resistor 90, while a minimum pulse duration is established by the value of capacitor 88 and the resistor 84.

Upon energization of the relay coil 86 closing the normally open relay switch 82, the positive terminal of the DC voltage source is connected through resistor 94 to one terminal of a second relay coil 96, the other terminal of which is connected to the negative terminal of the voltage source. The terminals of the relay coil 96 are shunted by a second time delay capacitor 98 in parallel with resistor 100 and adjustable resistor 102. Thus, upon closing of the normally open relay switch 82, an energizing circuit is completed for the relay coil 96 to cause energization thereof after a second time delay determined by the capacitor 98 and the setting of the adjustable resistor 102. The resistor 100 limits the current flow to protect relay coil 86 from high current damage.

Energization of the relay coil 96 after the second time delay, actuates its relay switch 80 to open the energizing circuit for the relay coil 86. When actuated, the relay switch 80 also connects the positive terminal of the DC voltage source through a voltage reducing resistor 104 to one terminal of a voltage isolating relay coil 106, the other terminal of which is connected to the negative terminal of the DC voltage source. The terminals of the relay coil 106 are shunted by a transient voltage-suppressing capacitor 108. It will therefore be apparent that energization of the relay coil 96 occurs after a second delay of sufficient duration to insure that the product has cleared the sizing station as diagrammed in FIG. 4 showing the beginning of pulse 44 spaced from the exposure period 36. Deenergization of the relay coil 86 at that time deactivates the transistor 70 and relay so as to allow completion of the cycle and permit the components to stabilize. Also, the relay coil 106 is energized to initiate the ejection period.

Upon energization of the voltage-isolating relay coil 106, the normally opened relay switch 110 associated therewith is closed to supply triggering current from the AC voltage source 60 through voltage reducing resistors 112 and 114 to the control electrode of a triac 116. Energizing current will then be transmitted by the triac from the voltage source 60 to the ejector solenoid 34. Transient line voltage protection is provided for the triac 116 by resistor 118 and capacitor 120 connected in series with each other across the triac input and output terminals.

It will be appreciated that the foregoing operation occurs only if the power switch 54 is closed connecting the neon lamp 122 across the terminals of the AC voltage source 60 so as to provide an indication that power is available. Another neon lamp 124 is connected across the terminals of the ejector solenoid 34 and will flash each time the circuit cycles or will stay on if the winding of the solenoid 34 is open. Thus, the lamp 124 provides an indication that a product is being sized. The ejector solenoid 34 may either control an air valve, nozzle or other electromechanical means associated with the ejector mechanism for removing products from the conveyor.

With the mode selector switch 66 in the "off" position engaging contact 64, only the cell 20 will be effective to hold a reverse bias on the base of transistor 70 until it is covered by the shadow of the product initiating an operational cycle. Through adjustable resistors 92 and 102, the duration of the cycle from start to the beginning of the ejection period may be adjusted. It should be appreciated that for this adjustment, the photocell 20 is on the downstream side of the sizing head relative to the direction of travel of the conveyor. It will also be apparent that the cycle beings only if the reject cells 28, 30 and 32 are not covered by the product shadow when the photocell 20 becomes covered by the shadow. When the mode switch 66 is displaced to the "on" position engaging contact 68, all of the inside photocells 20, 22 and 24 must be covered by the shadow to enable initiation of a cycle, to completely remove the negative reverse bias from the base of the transistor 70 which then becomes conductive to begin a signal pulse in view of the forward bias applied thereto through relay switch 80 and resistors 76 and 78. The relay coils 86 and 96 are then sequentially energized as aforementioned before the ejection period is begun by energization of the relay coil 106 supplying triggering voltage to the triac 116 operating as a power switch to conduct current to the ejector solenoid 34. The relay-energizing pulse 44 for the relay coil 96 is of short duration sufficient to condition the circuit for automatic reset at the end of the ejection period or ejector solenoid pulse 46. Operation of the circuit may be monitored by the neon lamps 122 and 124, lamp 124 indicating when the circuit is undergoing an operational cycle.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Claims

What is claimed as new is as follows:

1. In combination with a conveyor moving articles past at least one sizing station, apparatus for removing articles of a predetermined size and shape from the conveyor including means for sensing the presence of an article at the sizing station, pulse generating means connected to the sensing means for producing a signal pulse of a duration dependent upon the size, shape and speed of the article approaching and departing from the sizing station, means for terminating said signal pulse following departure of the article from the sizing station, ejector means rendered operative to displace the article from the conveyor during an ejection period of predetermined duration, and means responsive to termination of said signal pulse for rendering the ejector means operative.

2. The combination of claim 1 wherein said sensing means includes a first set of spaced photoresponsive devices having sensing faces aligned in a common plane parallel to the direction of movement of the article, disabling means connecting said first set of photoresponsive devices to the pulse-generating means for normally preventing development of the signal pulse, a second set of spaced photoresponsive devices having sensing faces aligned in said common plane, and means connecting the second set of photoresponsive devices to the pulse-generating means for limiting the strength of the signal pulse.

3. The combination of claim 2 wherein the sensing means further includes a source of radiation adapted to be blocked by the article and detected by the photoresponsive devices, and means for directing the radiation from said source onto the common plane intersecting the article while at the sizing station, whereby only articles at the sizing station having said predetermined size and shape prevent radiation from impinging on the first set of photoresponsive devices.

4. The combination of claim 3 wherein said second set of photoresponsive devices are adjustably positioned relative to the first set of photoresponsive devices.

5. The combination of claim 4 wherein said pulse generating means includes a source of control voltage, a current control device having power electrodes connected in series with the second set of photoresponsive devices to the source and a control electrode connected to the source, said first set of photoresponsive devices being interconnected in parallel by the disabling means to the control electrode.

6. The combination of claim 5 wherein said signal pulse terminating means includes relay means for disconnecting the source from the power electrodes when energized, and time delay means for energizing the relay means in delayed response to conduction of current through the current control device.

7. The combination of claim 6 including indicating means connected to the ejector means and rendered operative during the entire operational cycle.

8. The combination of claim 1 wherein said sensing means includes a first group of cells from which radiation is blocked, during an operational interval, by articles corresponding to shadows of predetermined size and shape and a second group of cells exposed to radiation during said operational interval.

9. In combination with a conveyor continuously moving articles along a path of travel past at least one sizing station, apparatus for gauging the size and shape of said articles at the sizing station including a source of radiation laterally spaced from the conveyor at the sizing station, a radiation receiving surface spaced from said path of travel onto which a shadow is projected by the source of radiation during movement of each of said articles at the sizing station, a plurality of accept cells having radiation-sensing faces in the plane of said receiving surface, a plurality of reject cells closely spaced from said accept cells, means responsive to covering of all of the accept cells by the shadows of said articles during operational intervals at the sizing station for generating signals, means responsive to covering of at least one of the reject cells by said shadows during said operational intervals for preventing operation of the signal-generating means, delay means for delaying operation of the signal generating means until each article passes the sizing station, and delay means for delaying operation of the signal generating means until a preceding one of the articles passes the sizing station.