Anti-dither container counter

A first sensor at a first location along a conveyor provides a first signal indicating whether or not a container is present at the first location while a second sensor similarly provides a second signal indicating whether or not a container is present at a second nearby location. The first and second signals are input to a logic circuit which outputs a count pulse only if the the inputs are of a proper form in a proper sequence designed so that dither is ignored. The sensors are diffuse reflection type sensors operating at different frequencies. They are mounted so their sensing axes converge at about a 15 degree angle and the sensor lenses are about 3.5 inches from the point of conveyance. A mounting system allows the sensors to be moved up/down and in/out with respect to the conveyor and maintain a position perpendicular with both the container sidewall and the container flow direction.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention, in general, relates to devices for counting containers, such 
as glass bottles, and more particularly, a counter that provides an 
accurate count of containers even when containers dither on their 
conveyor. 
2. Description of the Prior Art 
Accurate, non-contact counting of containers is essential in many 
industrial applications. For example, in the glass container industry 
production analyzing systems require accurate infeed and outfeed container 
counts to generate precise reports of container losses on various 
inspection and container handling devices along the production line. 
Dither has always presented a difficult problem for such counters. Dither 
occurs when the flow of containers is impeded and the conveyor continues 
to run. There are a myriad of reasons for this condition to take place: 
inspection equipment jams, flow control devices, conveyor jams, etc. 
Another common occurrence of container dither is caused by inspection and 
container handling devices that incorporate infeed screws. As the infeed 
screw rotates to feed containers into the equipment, pulsations are 
introduced back into the containers upstream of the device. Up to now, all 
counting systems, including those based on sonic, through beam, diffuse 
reflection, triple beam and retroreflective sensors have produced multiple 
"counts" for a single container when the container dithers on the sensing 
edge of the container counting device. In the prior art, a technique 
called blanking has been used to attempt to solve this problem. In this 
technique, the counter is blanked for a predetermined short time period 
after each count. However, systems that incorporate blanking do not work 
well, as they are sensitive to the normal line speed variation which 
occurs continuously in bottle handling systems. Thus it would be highly 
desirable to provide a container counter that does not produce multiple 
counts when containers dither. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a container counter that is 
highly accurate even when the containers dither. 
It is a further object of the invention to provide the above object in a 
container counter that is not sensitive to line speed variation. 
It is a further object of the invention to provide one or more of the above 
objects in a container counter that is highly reliable. 
It is another object of the invention to provide one or more of the above 
objects in a container counter that can be used with containers of a wide 
variety of shapes and sizes and made of a variety of materials. 
The invention provides a container counting apparatus for counting 
containers being conveyed on a means for conveying, said counter 
comprising: first sensor means for sensing the presence of a container at 
a first location and for providing a first signal representative of 
whether the container is present at said first location; second sensor 
means for sensing the presence of said container at a second location and 
for providing a second signal representative of whether the container is 
present at said second location; and logic means responsive to said first 
and second signals for providing a container counted signal for each 
container that passes by said first and second locations and for 
preventing additional bottle counted signals when a container dithers on 
said means for conveying. Preferably, the logic means comprises means for 
preventing additional bottle counted signals when a container dithers at 
said first location, said second location or in between said first and 
second locations. Preferably, said first sensor means senses along a first 
sensing axis and said second sensor means senses along a second sensing 
axis, and said first and second axes converge at an angle of substantially 
15.degree.. Preferably, said first sensor means comprises means for 
producing and detecting radiation of a first frequency and said second 
sensor means comprises means for producing and detecting radiation of a 
second frequency different from said first frequency. Preferably, said 
containers are glass bottles. 
The invention not only provides a container counter that is not affected by 
dither, but also provides one that is relatively easy to set up, operate 
and maintain. Numerous other features, objects and advantages of the 
invention will become apparent from the following detailed description 
when read in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Directing attention to FIG. 1, a perspective diagrammatic view of the 
apparatus 10 of the invention being employed in conjunction with a glass 
bottle conveyor 12. It should be understood that the particular embodiment 
of the invention shown in FIG. 1 and the other FIGS. is intended to be 
exemplary only, is shown only to illustrate the invention, and is not 
intended to limit the invention to the particular details of the 
embodiment. The conveyor comprises a conveyor belt 14 and conventional 
structure supporting and driving it, which structure is not shown for 
clarity. A bottle 15 is conveyed by the conveyor 12 past the counter 10 of 
the invention. Counter 10 comprises a first sensing means 17, second 
sensing means 18, logic means 20, a support 21, and a mounting means 22 
for adjustably mounting the support 21 and sensing means 17 and 18 on the 
conveyor 12. The means 22 comprises a means 25 for vertically adjusting 
the height of the sensing means 17 and 18 with respect to the conveyor and 
a means 26 for adjusting the distance of the sensing means 17 and 18 to 
the conveyor. The mounting means 22 is attached to the conveyor support 
structure which is not shown. The invention also may include means for 
individually adjusting the position, including the angle with the 
perpendicular to the line of bottle motion, of each of the sensors 17 and 
18. The mounting means 22 permits the sensors 17 and 18 to move up and 
down and in and out with respect to the conveyor 12 and at the same time 
maintain a position perpendicular both with the container sidewall and the 
container flow direction 40 (FIG. 3). Since the sidewall of the preferred 
container, a glass bottle 15, is curved and the sensors 17 and 18 are 
spaced apart they must be at an angle to one another if each is to be 
perpendicular to the container sidewall. 
In the preferred embodiment, each of the sensor means 17 and 18 is a 
diffuse reflection type sensor, each operating at a different frequency. 
The preferred embodiment sensor means is a Keyence Model PZ-41 available 
from Keyence Corporation of America, 20610 Manhattan Place, Suite 132, 
Torrence, CA 90501. Each sensor 17 and 18 has a light source and a light 
detector enclosed within a casing 27 and 28 respectively, and a lens 30 
and 31 respectively. The positioning of the sensors 17 and 18 with respect 
to one another and the bottle 15 is seen better in FIGS. 3 through 7. 
Referring to FIG. 3, first sensor means 17 senses along a first sensing 
axis 34, second sensor means 18 senses along a second sensing axis 35. It 
has been found that optimum results are obtained if the axis 34 and axis 
35 converge at an angle of 15.degree. and the lenses 30 and 31 are located 
a length L, 3.5 inches from the point 50 of convergence. Preferably, the 
convergence point is beyond the center line of the container. These 
dimensions permit a wide range of container diameters. It is understood 
that these dimensions can vary however. As shown in FIGS. 3 through 7, 
each of the sensor means 17 and 18 include an LED, 43 and 44 respectively, 
which indicates when the sensor is sensing the presence of a container. 
Sensor means 17 is connected to logic means 20 via electrical cable 46 
while sensor means 18 is connected to logic means 20 via electrical cable 
47. The logic means 20 is preferably an electrical circuit as shown in 
FIG. 2. The circuit preferably comprises NAND gates 51 through 54, NOR 
gate 56, inverters 58 through 60, flip-flops 61 and 62, and one-shot 64. 
The inputs are labeled A and B while the output is labeled C. 
The counter according to the invention operates as follows. The sensor 
means support 21 is positioned to be perpendicular to both the container 
sidewall and the container flow direction 40, which is from top to bottom 
in FIGS. 3 through 7. The support 21 is adjusted in the in/out direction 
via the adjusting means 26 so that the following sequence of sensor means 
17 and 18 activity occurs when a container traverses the sensor means 
arrangement: The upstream sensor means 17, hereinafter and in FIGS. 3 
through 9 referred to as sensor A so as to correspond to the input A of 
FIG. 2, detects the container, followed by detection by the downstream 
sensor means 18, hereinafter and in FIGS. 3 through 9 referred to as 
sensor B. Next sensor A detects the absence of a container followed by 
sensor B detecting the absence of a container. For this sequence to be 
correct, the convergence point must be beyond the center line of the 
container. Note that the in/out adjustment of support 21 does not change 
the length L. This activity causes the logic means 20 to produce one count 
pulse on output C and reset itself in preparation for the next container. 
As will be shown in detail below, the logic means circuit 20 is designed 
to ignore leading and trailing edge dither on both sensors A and B. By 
design, no adjustment is necessary for container flow speed variation. 
FIGS. 3 through 7 and the truth tables in FIGS. 8 and 9 further illustrate 
the invention. In each of the FIGS. 3 through 7, the output of the sensors 
A and B are indicated by the status of the LED's 43 and 44. For example in 
FIG. 4, LED 43 is on indicating sensor A has changed to a "low" or "logic 
0" signal indicating it is detecting the presence of a bottle, while LED 
44 is off indicating that sensor B is inputting to the logic means 20 a 
"high" or "logic 1" signal indicating it is detecting the absence of a 
bottle. In the truth table of FIG. 8, the signals on inputs A and B and 
output C of logic circuit 20 are summarized for each of the FIGS. 3 
through 7. The signals are shown as a logic 1, logic 0, in transition from 
low to high (logic 0 to logic 1) as for example the entry under column A 
for FIG. 6, in transition from high to low (logic 1 to logic 0) as in the 
entry under column A for FIG. 4, or as a one-shot pulse, as the entry 
under column C for FIG. 5. In FIGS. 3 through 7, the solid "container" 
lines represent present container position while the dashed "container" 
lines represent the container's previous position. For example, in FIG. 4, 
the container has just moved from the dashed position to the solid 
position. FIG. 8 illustrates the truth table for the situation where the 
container 15 passes smoothly from a position upstream of both sensors A 
and B to a position downstream of both sensors with no dither. 
FIG. 9 shows the output of the logic circuit 20 in the cases where there is 
dither at the leading and trailing edges for each sensor. The entries for 
FIGS. 3 through 7 given in FIG. 8 are also included for reference. For 
each row, an analysis of the response of the circuit components 51 through 
54, 56, 58, 59, 60, 61, 62 and 64 of FIG. 2 to the A and B inputs shown, 
gives the output shown in column C. It is seen that the logic circuit 20 
generates a count pulse only when its A and B inputs receive high to low 
and low to high transitions in the proper sequence. Thus it is seen that 
in all cases the dither is ignored by the circuit. In all cases, the 
one-shot produces only one pulse indicating one count. Thus the invention 
counts each container 15 once and only once. 
A novel apparatus for counting containers that accurately counts containers 
even in the presence of dither has been described. It is evident that 
those skilled in the art may now make numerous uses and modifications of 
and departures from the specific embodiment described herein without 
departing from the inventive concepts. For example, the various electronic 
components can be replaced with equivalent electronic parts. The 
mechanical parts may be made differently to perform equivalent functions. 
Many other variations may be described. Consequently, the invention is to 
be construed as embracing each and every novel feature and novel 
combination of features present and/or possessed by the container counter 
described.