Title:
ARTICLE ARRANGING AND COUNTING MACHINE
United States Patent 3730386
Abstract:
A cascade of vibratory conveyors receive discrete fragile articles in bulk and by operating successive conveyors at higher rates the articles are delivered in a single row to a rotary brush which accelerates successive articles to provide spaces between them. The spaced articles are photoelectrically counted and dropped onto a bottom closure in a receiver. After a predetermined count a partition is interposed in the receiver to temporarily intercept and hold further articles, while feeding and counting continues, until the articles on the closure have been discharged and the closure returned to closed position. A portion of one of the conveyors is so narrow it can hold only a single row of articles.
US Patent References:
Small photosensitive article counter
Lakso et al. - September 1965 - 3207909
APPARATUS FOR STACKING AND PACKING CYLINDRICAL OR ROD-SHAPED WORKPIECES
Strohmeier et al. - October 1970 - 3535847
Small photosensitive article counter
Lakso et al. - September 1965 - 3207909
APPARATUS FOR STACKING AND PACKING CYLINDRICAL OR ROD-SHAPED WORKPIECES
Strohmeier et al. - October 1970 - 3535847
Application Number:
05/141690
Publication Date:
05/01/1973
Filing Date:
05/10/1971
View Patent Images:
Export Citation:
Assignee:
Wright Machinery Company, Inc. (Durham, NC)
Primary Class:
Other Classes:
53/500, 198/453, 198/444
International Classes:
B65G47/14
Field of Search:
221/12,206,207,201 235/92 198/33AA,30
Primary Examiner:
Tollberg, Stanley H.
Claims:
I claim
1. In an article arranging and counting machine:
2. A machine as defined in claim 1 wherein said first conveyor is arranged to discharge articles from said extension onto said second conveyor, said second conveyor being of a width substantially the same as the width of said extension.
3. A machine as defined in claim 1 wherein said extension tapers, in width, forwardly to a minimum width at the forward end thereof substantially equal to the width of the articles to be conveyed; and wing panels extending downwardly and outwardly from the tapering side edges of said extension.
4. A machine as defined in claim 3 wherein said extension overlies an end portion of said second conveyor.
5. A machine as defined in claim 1 wherein said counting means comprises a rotatable brush arranged to receive thereon articles discharged from said second conveyor; means for rotating said brush at a speed to accelerate articles deposited thereon and thereby provide space between successive articles; and photoelectric means for counting the articles so spaced.
6. In a machine having an article counter and means for sequentially delivering single discrete articles to said counter to be counted thereby and a receiver arranged to receive articles from said counter, the improvement comprising:
7. A machine as defined in claim 6 wherein said actuating means include pneumatic motor devices drivingly connected to said partition and to said bottom closure.
8. A machine as defined in claim 6 wherein said partition comprises a plate member pivotal about a generally horizontal axis extending through said chamber, said first position being wherein said plate member extends generally vertically and said second position being wherein said plate member extends across said chamber sufficiently to intercept and hold said articles.
1. In an article arranging and counting machine:
2. A machine as defined in claim 1 wherein said first conveyor is arranged to discharge articles from said extension onto said second conveyor, said second conveyor being of a width substantially the same as the width of said extension.
3. A machine as defined in claim 1 wherein said extension tapers, in width, forwardly to a minimum width at the forward end thereof substantially equal to the width of the articles to be conveyed; and wing panels extending downwardly and outwardly from the tapering side edges of said extension.
4. A machine as defined in claim 3 wherein said extension overlies an end portion of said second conveyor.
5. A machine as defined in claim 1 wherein said counting means comprises a rotatable brush arranged to receive thereon articles discharged from said second conveyor; means for rotating said brush at a speed to accelerate articles deposited thereon and thereby provide space between successive articles; and photoelectric means for counting the articles so spaced.
6. In a machine having an article counter and means for sequentially delivering single discrete articles to said counter to be counted thereby and a receiver arranged to receive articles from said counter, the improvement comprising:
7. A machine as defined in claim 6 wherein said actuating means include pneumatic motor devices drivingly connected to said partition and to said bottom closure.
8. A machine as defined in claim 6 wherein said partition comprises a plate member pivotal about a generally horizontal axis extending through said chamber, said first position being wherein said plate member extends generally vertically and said second position being wherein said plate member extends across said chamber sufficiently to intercept and hold said articles.
Description:
BACKGROUND OF THE INVENTION
This invention is in the field of article arranging and counting machines, particularly machines for counting discrete articles and assembling separate groups of predetermined numbers of such articles.
The arranging of articles in single file and counting the same for packaging in quantities of predetermined numbers is known to the art, but machines for arranging such articles in single file arrangement and counting them into predetermined groups has heretofore involved the design of machines specifically and peculiarly adapted to the particular articles and were generally of little or no utility for counting different types of articles. Furthermore, no such apparatus is known which could arrange, count and assemble in groups, fragile articles subject to damage by rough handling.
SUMMARY OF THE INVENTION
The present invention is described with reference to the counting and segregating of egg rolls, specifically, but the articles referred to in the description are merely by way of illustration and representative of other fragile articles adapted to be counted by the present invention. Clearly, however, non-fragile articles could be processed by the machine to be described.
The machine comprises a cascade of vibratory conveyors in which the articles tend to gravitate toward the longitudinal center line thereof. The conveyors are operated at successively higher rates, thus tending to spread the articles out and arrange them in single file order. The "rate" of operation of a conveyor is intended to refer to the rate of advance of articles thereon, whether it be dependent on the speed of vibration or the amplitude thereof, or both. The final conveyor of the group is of a width only great enough to support a single row of the articles and they are delivered therefrom onto the periphery of a rotating brush which accelerates each article delivered to it to spatially separate it from following articles and project it through the beam of a photoelectric counting means.
The articles so counted are dropped into a receiver and when a predetermined count has been collected in the receiver a partition therein is moved to intercept further articles and hold them in an upper compartment formed thereby while counting continues and until the previously counted group have been discharged, whereupon the accumulated articles are moved to the lower compartment in preparation for achieving a final count and repetition of the cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a pictorial view of an arranging and counting machine embodying the present invention;
FIG. 2 is a side elevational view of the machine of FIG. 1;
FIG. 3 is an enlarged fragmentary transverse sectional view taken on the line 3--3 of FIG. 2;
FIG. 4 is an enlarged fragmentary plan view, partly in section, taken on the line 4--4 of FIG. 3;
FIG. 5 is an enlarged fragmentary vertical sectional view taken on the line 5--5 of FIG. 3; and
FIG. 6 is a perspective view of the control panel for the machine.
DESCRIPTION OF A PREFERRED EMBODIMENT
In the drawings numeral 2 designates generally a suitable framework supporting the various components of the machine to be described. On the framework 2 there is mounted a hopper 4 adapted to receive a bulk quantity of articles to be processed and to deliver the same through a discharge chute 6 to a first conveyor 8. The conveyor 8 is the first of a cascaded series of conveyors 8, 10 and 12, each of which is a well known type of conveyor comprising a suitable base 14, resilient supporting reeds 16 and a magnetic vibratory motor device 18 adapted to cause the vibrator trough 20 to vibrate in a generally fore and aft direction. As is evident from the drawings, at least the troughs of conveyors 10 and 12 are of generally V-shape in cross-section so that articles being moved thereby tend to gravitate toward the center line thereof.
As shown, the chute 6 delivers articles in a bulk stream to the first conveyor 8. The conveyor 8 is operated at such a rate that it tends to accelerate the articles 22 and when those articles are delivered into the conveyor 10, which is normally operated at a still higher rate, the articles try to assume a single file arrangement and, due to the shape of the conveyor 10, substantially such a single file arrangement is normally achieved at about the discharge end 24 thereof. A narrow extension 26 is formed on the forward end of the trough of conveyor 10 and, as shown, particularly in FIG. 1, that extension is quite narrow, its average width being not materially greater than the corresponding dimension of the articles 22 thereon. Thus, if two articles try to occupy the extension 26 in side-by-side or superimposed relation, one of them will fall laterally off that extension, being guided by wings 25 into a receiving hopper 27 or 28 whereby it is directed to a suitable receiver receptacle 30 (see FIG. 2) for recycling. Obviously, the receptacle 30 could be replaced by a suitable conveyor to return such articles to the hopper 4. As shown, the narrow extension 26 tapers somewhat in a forward direction. Its minimum width at its forward end being no greater than the corresponding dimension of an article 22 and the wings 25 slope downwardly and outwardly to direct excess articles into the hopper 26 or hopper 28.
The last or most forward conveyor 12 thus receives only a single file row of articles 22. If, by any chance, side-by-side articles should reach the conveyor 12, the width thereof is such that one of such articles would drop therefrom into one of the hoppers 27 or 28 and only a single file row of articles can be discharged by the conveyor 12. Articles delivered from the discharge end of conveyor 12 are immediately engaged by the bristles 32 of a rotary brush 33. The brush 33 having the bristles 32 includes side plates 34 mounted on a suitable shaft 36 journalled in frame 2 and driven by motor 38. The speed of rotation of the brush 33 is such that the peripheral speed of the bristles 32 is greater than the speed of the articles 22 delivered from conveyor 12 and thus each article is accelerated by the brush to provide a space between that article and the next following article, all as clearly evident from FIG. 5.
As stated previously, the description herein relates to the arranging and counting of articles 22, which in this instance are considered to be egg rolls, a relatively fragile food product. Obviously, the vibratory conveyors 8, 10 and 12 have no tendency to damage the fragile products and the provision of the rotary brush 33 having bristles 32 further ensure that the articles will not be damaged at this point in their processing.
A support bar 40 is carried by adjustable brackets 42 mounted on the frame 2 and by means of brackets 44 the bar 40 supports a light source 46, and a photocell 48. The light source 46 directs a beam of light across the path of movement of articles 22 closely adjacent the periphery of the brush bristles 32, as shown in FIG. 5. As is also clear from FIG. 5, each article 22 engaged by the bristles 32 and separated from its following article is caused to move through the beam of light and interrupt its impingement on photocell 48 and suitable circuits, well known to those skilled in the art, effect indication on a register 50 (see FIG. 6) of the number of articles thus counted.
After the articles 22 pass through the counter beam, as described, they fall by gravity generally along the path indicated by arrows 52 in FIG. 5. Arranged below the rotary brush and across the path of the falling articles is a receiver 54 having side walls 56 and a pivoted bottom closure 58. The closure 58 is normally in its closed position as shown in solid lines in FIG. 5. A transverse rockable shaft 60 extends laterally across the interior of the receiver 54 and has fixed thereon, within the receiver, a partition member 62 comprising a pair of planar portions extending substantially the full width of the receiver 54. The partition member 62 is normally held in the generally vertical position shown by solid lines in FIG. 5.
A pneumatic motor device 64 is pivoted to the frame 2 on an axis 66 and is supplied with operating fluid through conduits 68. The motor device 64 comprises a double-acting piston therein having a piston rod 70 pivotally connected, at 72, to the closure 58, whereby actuation of the motor device 64 to its illustrated position moved the closure 58 into closing relation to the receiver 54 and movement of the piston to the left swings the closure 58 to the open position shown by dotted lines in FIG. 5.
The transverse rock shaft 60 has a crank arm 74 fixed thereto outside the receiver 54 and a second pneumatic motor device 76, similar to the pneumatic motor 64, has its piston rod 78 pivotally connected to the outer end of crank arm 74. The motor device 76 is pivotally mounted on the frame 2 on an axis at 80. As is obvious, extension of the motor device 76 rocks the shaft 60 counterclockwise to position the partition member 62 in the generally vertical position shown in FIG. 3 by solid lines whereas contraction of the motor device 76 swings rock shaft 60 clockwise to position the partition member 62 in the dotted line position shown. As is obvious, the articles 22 falling into receiver 54 will drop to the bottom thereof, past the partition member 62 when the latter is in its generally vertical position and such articles accumulate in the bottom of the receiver 54, resting on the closed closure 58. When the partition member 62 is swung to its dotted line position, it effectively divides the receiver 54 into upper and lower compartments, the lower compartment being adjacent the closure 58 and the upper compartment being that region above the partition member 62. When in its dotted line position, the partition member 62 will intercept all articles 22 falling from the rotary brush 33 and will hold them in the so-called upper compartment until released therefrom.
FIG. 6 illustrates, schematically, the face of a control panel 82, mounted on the frame 2, as shown in FIG. 1. The control panel 82 provides controls for the various functions of the machine, including a main switch 84, a switch 86 for controlling power to the vibratory conveyors, and controls 88, 90 and 92, respectively, regulating the rates of operation of vibratory conveyors 8, 10 and 12.
In operation, the vibratory conveyors continuously receive articles 22 from the chute 6 of hopper 4 and advance the same, ultimately arranging them in a single file row as described, and successive articles are then delivered to the rotary brush 33 which spatially separates them and effects their counting in the manner described. By suitable settable means (not shown) obvious to those skilled in the art, the achievement of a predetermined count of articles and accumulation of such predetermined number of articles in the lower portion of receiver 54 causes actuation of a suitable air control valve to first contract pneumatic motor 76 and thus swing partition member 62 to the dotted line position of FIG. 5 whereupon all further articles delivered to the receiver are intercepted and retained in the upper compartment previously described while a predetermined number of articles are adjacent the closure 58. Thereafter, the control valve arrangement referred to is actuated to deliver air under pressure to the right hand conduit 68 leading to motor 64 and thus swing the closure 58 to its open position and discharging from the receiver 54 the accumulated group of articles 22 of a predetermined number in the closure compartment. Thereafter, the motor 64 is actuated to close closure 58 and to return partition member 62 to its generally upright position whereupon the articles previously intercepted and retained on that partition member are dropped into the lower compartment and are held by closure 58. During the above described operations the conveyors 8, 10 and 12 continue to advance, separate and count articles 22 and are continuously operating without interruption during discharge of the accumulated articles from the receiver and the machine thus arranges and counts articles continuously while periodically discharging only groups containing the required number of articles.
As shown in the drawings, particularly FIG. 4, the trough of conveyor 10 is preferably provided with a pair of openings 94 in lateral alignment and through which a light source 96 projects a beam of light to a photocell 98. The openings 94 are so positioned that the beam of light referred to extends across the trough of conveyor 10 adjacent the top thereof. In the event articles 22 should accumulate on conveyor 10 in excessive numbers, the beam of light referred to would be intercepted and the photocell 98 controls a circuit (not shown) to interrupt the operation of the conveyors so that the excessive number of articles on conveyor 10 is reduced sufficiently to reestablish the light beam whereupon normal operation is resumed.
While a single specific embodiment of the invention has been shown and described herein, the same is merely illustrative of the principles involved and other embodiments may be resorted to within the scope of the appended claims.
This invention is in the field of article arranging and counting machines, particularly machines for counting discrete articles and assembling separate groups of predetermined numbers of such articles.
The arranging of articles in single file and counting the same for packaging in quantities of predetermined numbers is known to the art, but machines for arranging such articles in single file arrangement and counting them into predetermined groups has heretofore involved the design of machines specifically and peculiarly adapted to the particular articles and were generally of little or no utility for counting different types of articles. Furthermore, no such apparatus is known which could arrange, count and assemble in groups, fragile articles subject to damage by rough handling.
SUMMARY OF THE INVENTION
The present invention is described with reference to the counting and segregating of egg rolls, specifically, but the articles referred to in the description are merely by way of illustration and representative of other fragile articles adapted to be counted by the present invention. Clearly, however, non-fragile articles could be processed by the machine to be described.
The machine comprises a cascade of vibratory conveyors in which the articles tend to gravitate toward the longitudinal center line thereof. The conveyors are operated at successively higher rates, thus tending to spread the articles out and arrange them in single file order. The "rate" of operation of a conveyor is intended to refer to the rate of advance of articles thereon, whether it be dependent on the speed of vibration or the amplitude thereof, or both. The final conveyor of the group is of a width only great enough to support a single row of the articles and they are delivered therefrom onto the periphery of a rotating brush which accelerates each article delivered to it to spatially separate it from following articles and project it through the beam of a photoelectric counting means.
The articles so counted are dropped into a receiver and when a predetermined count has been collected in the receiver a partition therein is moved to intercept further articles and hold them in an upper compartment formed thereby while counting continues and until the previously counted group have been discharged, whereupon the accumulated articles are moved to the lower compartment in preparation for achieving a final count and repetition of the cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a pictorial view of an arranging and counting machine embodying the present invention;
FIG. 2 is a side elevational view of the machine of FIG. 1;
FIG. 3 is an enlarged fragmentary transverse sectional view taken on the line 3--3 of FIG. 2;
FIG. 4 is an enlarged fragmentary plan view, partly in section, taken on the line 4--4 of FIG. 3;
FIG. 5 is an enlarged fragmentary vertical sectional view taken on the line 5--5 of FIG. 3; and
FIG. 6 is a perspective view of the control panel for the machine.
DESCRIPTION OF A PREFERRED EMBODIMENT
In the drawings numeral 2 designates generally a suitable framework supporting the various components of the machine to be described. On the framework 2 there is mounted a hopper 4 adapted to receive a bulk quantity of articles to be processed and to deliver the same through a discharge chute 6 to a first conveyor 8. The conveyor 8 is the first of a cascaded series of conveyors 8, 10 and 12, each of which is a well known type of conveyor comprising a suitable base 14, resilient supporting reeds 16 and a magnetic vibratory motor device 18 adapted to cause the vibrator trough 20 to vibrate in a generally fore and aft direction. As is evident from the drawings, at least the troughs of conveyors 10 and 12 are of generally V-shape in cross-section so that articles being moved thereby tend to gravitate toward the center line thereof.
As shown, the chute 6 delivers articles in a bulk stream to the first conveyor 8. The conveyor 8 is operated at such a rate that it tends to accelerate the articles 22 and when those articles are delivered into the conveyor 10, which is normally operated at a still higher rate, the articles try to assume a single file arrangement and, due to the shape of the conveyor 10, substantially such a single file arrangement is normally achieved at about the discharge end 24 thereof. A narrow extension 26 is formed on the forward end of the trough of conveyor 10 and, as shown, particularly in FIG. 1, that extension is quite narrow, its average width being not materially greater than the corresponding dimension of the articles 22 thereon. Thus, if two articles try to occupy the extension 26 in side-by-side or superimposed relation, one of them will fall laterally off that extension, being guided by wings 25 into a receiving hopper 27 or 28 whereby it is directed to a suitable receiver receptacle 30 (see FIG. 2) for recycling. Obviously, the receptacle 30 could be replaced by a suitable conveyor to return such articles to the hopper 4. As shown, the narrow extension 26 tapers somewhat in a forward direction. Its minimum width at its forward end being no greater than the corresponding dimension of an article 22 and the wings 25 slope downwardly and outwardly to direct excess articles into the hopper 26 or hopper 28.
The last or most forward conveyor 12 thus receives only a single file row of articles 22. If, by any chance, side-by-side articles should reach the conveyor 12, the width thereof is such that one of such articles would drop therefrom into one of the hoppers 27 or 28 and only a single file row of articles can be discharged by the conveyor 12. Articles delivered from the discharge end of conveyor 12 are immediately engaged by the bristles 32 of a rotary brush 33. The brush 33 having the bristles 32 includes side plates 34 mounted on a suitable shaft 36 journalled in frame 2 and driven by motor 38. The speed of rotation of the brush 33 is such that the peripheral speed of the bristles 32 is greater than the speed of the articles 22 delivered from conveyor 12 and thus each article is accelerated by the brush to provide a space between that article and the next following article, all as clearly evident from FIG. 5.
As stated previously, the description herein relates to the arranging and counting of articles 22, which in this instance are considered to be egg rolls, a relatively fragile food product. Obviously, the vibratory conveyors 8, 10 and 12 have no tendency to damage the fragile products and the provision of the rotary brush 33 having bristles 32 further ensure that the articles will not be damaged at this point in their processing.
A support bar 40 is carried by adjustable brackets 42 mounted on the frame 2 and by means of brackets 44 the bar 40 supports a light source 46, and a photocell 48. The light source 46 directs a beam of light across the path of movement of articles 22 closely adjacent the periphery of the brush bristles 32, as shown in FIG. 5. As is also clear from FIG. 5, each article 22 engaged by the bristles 32 and separated from its following article is caused to move through the beam of light and interrupt its impingement on photocell 48 and suitable circuits, well known to those skilled in the art, effect indication on a register 50 (see FIG. 6) of the number of articles thus counted.
After the articles 22 pass through the counter beam, as described, they fall by gravity generally along the path indicated by arrows 52 in FIG. 5. Arranged below the rotary brush and across the path of the falling articles is a receiver 54 having side walls 56 and a pivoted bottom closure 58. The closure 58 is normally in its closed position as shown in solid lines in FIG. 5. A transverse rockable shaft 60 extends laterally across the interior of the receiver 54 and has fixed thereon, within the receiver, a partition member 62 comprising a pair of planar portions extending substantially the full width of the receiver 54. The partition member 62 is normally held in the generally vertical position shown by solid lines in FIG. 5.
A pneumatic motor device 64 is pivoted to the frame 2 on an axis 66 and is supplied with operating fluid through conduits 68. The motor device 64 comprises a double-acting piston therein having a piston rod 70 pivotally connected, at 72, to the closure 58, whereby actuation of the motor device 64 to its illustrated position moved the closure 58 into closing relation to the receiver 54 and movement of the piston to the left swings the closure 58 to the open position shown by dotted lines in FIG. 5.
The transverse rock shaft 60 has a crank arm 74 fixed thereto outside the receiver 54 and a second pneumatic motor device 76, similar to the pneumatic motor 64, has its piston rod 78 pivotally connected to the outer end of crank arm 74. The motor device 76 is pivotally mounted on the frame 2 on an axis at 80. As is obvious, extension of the motor device 76 rocks the shaft 60 counterclockwise to position the partition member 62 in the generally vertical position shown in FIG. 3 by solid lines whereas contraction of the motor device 76 swings rock shaft 60 clockwise to position the partition member 62 in the dotted line position shown. As is obvious, the articles 22 falling into receiver 54 will drop to the bottom thereof, past the partition member 62 when the latter is in its generally vertical position and such articles accumulate in the bottom of the receiver 54, resting on the closed closure 58. When the partition member 62 is swung to its dotted line position, it effectively divides the receiver 54 into upper and lower compartments, the lower compartment being adjacent the closure 58 and the upper compartment being that region above the partition member 62. When in its dotted line position, the partition member 62 will intercept all articles 22 falling from the rotary brush 33 and will hold them in the so-called upper compartment until released therefrom.
FIG. 6 illustrates, schematically, the face of a control panel 82, mounted on the frame 2, as shown in FIG. 1. The control panel 82 provides controls for the various functions of the machine, including a main switch 84, a switch 86 for controlling power to the vibratory conveyors, and controls 88, 90 and 92, respectively, regulating the rates of operation of vibratory conveyors 8, 10 and 12.
In operation, the vibratory conveyors continuously receive articles 22 from the chute 6 of hopper 4 and advance the same, ultimately arranging them in a single file row as described, and successive articles are then delivered to the rotary brush 33 which spatially separates them and effects their counting in the manner described. By suitable settable means (not shown) obvious to those skilled in the art, the achievement of a predetermined count of articles and accumulation of such predetermined number of articles in the lower portion of receiver 54 causes actuation of a suitable air control valve to first contract pneumatic motor 76 and thus swing partition member 62 to the dotted line position of FIG. 5 whereupon all further articles delivered to the receiver are intercepted and retained in the upper compartment previously described while a predetermined number of articles are adjacent the closure 58. Thereafter, the control valve arrangement referred to is actuated to deliver air under pressure to the right hand conduit 68 leading to motor 64 and thus swing the closure 58 to its open position and discharging from the receiver 54 the accumulated group of articles 22 of a predetermined number in the closure compartment. Thereafter, the motor 64 is actuated to close closure 58 and to return partition member 62 to its generally upright position whereupon the articles previously intercepted and retained on that partition member are dropped into the lower compartment and are held by closure 58. During the above described operations the conveyors 8, 10 and 12 continue to advance, separate and count articles 22 and are continuously operating without interruption during discharge of the accumulated articles from the receiver and the machine thus arranges and counts articles continuously while periodically discharging only groups containing the required number of articles.
As shown in the drawings, particularly FIG. 4, the trough of conveyor 10 is preferably provided with a pair of openings 94 in lateral alignment and through which a light source 96 projects a beam of light to a photocell 98. The openings 94 are so positioned that the beam of light referred to extends across the trough of conveyor 10 adjacent the top thereof. In the event articles 22 should accumulate on conveyor 10 in excessive numbers, the beam of light referred to would be intercepted and the photocell 98 controls a circuit (not shown) to interrupt the operation of the conveyors so that the excessive number of articles on conveyor 10 is reduced sufficiently to reestablish the light beam whereupon normal operation is resumed.
While a single specific embodiment of the invention has been shown and described herein, the same is merely illustrative of the principles involved and other embodiments may be resorted to within the scope of the appended claims.