Computerized combination weigher with preset optimum weigher discharge

A method and apparatus for weighing product for delivery to a package is disclosed. Product is fed from a main conveyor to a plurality of secondary conveyors, each of which is provided with an individual weighing station. Each weighing station includes upper and lower weighing units, each weighing unit comprising a gated hopper and a weighing cell. A local computer is provided at each weighing station and all of the local computers are connected to a main computer. In operation the upper weighing unit of each weighing station is set at a different predetermined fraction of the total desired package weight and when sufficient product is delivered to the upper weighing head of each weighing station the conveyor to such weighing station is stopped and the weighed product is delivered to the lower weighing head where the weight is checked. The main computer calculates the combination of weights in each weighing station to determine the combination most nearly equal to but not less than the desired final package weight. The fractional weights at which each weighing head is set may be adjusted up or down dependent upon the number of weighing stations utilized to make up the final package weight.

The present invention relates to a method and apparatus for weighing 
product to be delivered to an open package. 
There have been numerous attempts to increase the accuracy of weighing 
product to be delivered to open packages in connection with the use of 
packaging machines known as form, fill and seal machines. It is essential 
that the number of underweight packages be reduced as close to zero as 
possible and still minimize the number of substantially overweight 
packages. In the use of form, fill and seal packaging equipment it is also 
essential to weight and deliver the product to the open package as quickly 
as possible. 
One such method and apparatus for providing accurate weights expeditiously 
is disclosed in U.S. Pat. No. 3,939,928, issued Feb. 24, 1976. In this 
system a plurality of weighing heads are provided and the time of delivery 
of product of each of these weighing heads is varied so that each of the 
weighing heads receives a different quantity of product. The weight in 
each of the weighing heads is transmitted to a central computer which 
calculates the combination of weights of products in each of the weighing 
heads which most nearly equals the desired package weight. However, due to 
variations in the amount of product delivered by the conveyor to the 
weighing head it is not possible to accurately predict the amount of 
product delivered to each weighing head for a predetermined time period. 
Thus, wide flucuations in the weight of product received by each weighing 
head are experienced when operating with the method and apparatus 
described in the aforementioned patent. 
According to the present invention there is provided a method and apparatus 
for accurately obtaining exact package weights. There is provided a 
plurality of weighing stations, each weighing station including an upper 
and lower weighing unit and wherein precise predetermined fractional 
portions of the desired final weight are obtained in each weighing 
station. Each weighing station has the upper weighing unit set to receive 
a different fractional portion of the desired final weight. When this 
fractional weight is reached by the upper weighing unit the feed conveyor 
to that unit is stopped and the product is delivered to the lower weighing 
unit where the weight is checked. The check weight value is then 
transmitted to a central computer which then sums the weights from the 
various weighing stations and determines that combinations of weights 
which is not less than but most closely equal to the desired final package 
weight. 
The apparatus includes a main feed conveyor which delivers product to a 
central cone shaped disc which in turn delivers the product to secondary 
feed conveyors surrounding the central disc. The cone shaped disc may be 
orbitally moved so as to deliver product to the various secondary feed 
conveyors more evenly. Means is provided for determining the product 
buildup on the cone shaped disc so that the main feed conveyor may be 
shutoff when the heighth of product on the central disc reaches a 
predetermined value. Each of the weighing stations includes a pair of 
hoppers disposed one above the other and each weighing station includes 
two weighing units and a built in computer to provide information to the 
central computer as well as to control the cutoff signals to the secondary 
conveyors and operating signals to the gates on the weighing hoppers. The 
weighing stations may be readily removed from the apparatus and the 
delivery tube to the open package is centrally located and readily 
accessible by removal of the weighing stations. 
An object of the present invention is to provide a method and apparatus for 
achieving a high degree of accuracy in the weight of product delivered to 
a package. 
Further object of the present invention is to provide a method and 
apparatus for weighing a plurality of predetermined fractional portions of 
a desired final package weight and determining the combination of such 
predetermined fractional weights most nearly equal to but not less than 
the desired final package weight. 
Other objects and many of the intended advantages of the present invention 
will be apparent upon consideration of the following detailed 
specification and drawings.

Referring now more specifically to the drawings wherein like numerals refer 
to like parts throughout the several views, there is shown at 1 in FIG. 2 
a main feed conveyor which is provided with a vibrator 2 for delivering 
product from a feed belt (not shown) at the outer end of the conveyor to a 
central funnel 3. The funnel 3 delivers the product to a central cone 
shaped disc 4 which may be mounted for orbital movement beneath the funnel 
3. Surrounding the periphery of the disc 4 are a plurality of individual 
secondary feed conveyors 5 each of which has outwardly extending flanges 6 
which overlie the flanges on adjacent secondary feed conveyors. These 
conveyors are driven by vibratory motors such as shown at 7 to deliver 
product from their inner ends to the outer ends. 
It can be seen that the vibratory motor 7 and secondary conveyors 5 are 
mounted on a central platform 8 which is in turn supported by brackets 9 
which form part of the main frame of the apparatus. Similarly, a bracket 
10 having frame 11 on the outer end thereof supports the funnel 3 beneath 
the outlet of the main feed conveyor 1. 
There is also shown in FIG. 2 a photoelectric scanner 12 which serves to 
measure the depth of product accumulating on disc 4 and to shutoff the 
vibratory motor 2 delivering product on main feed conveyor 1 when the 
depth of product reaches a predetermined value. It is also possible to 
measure the depth of product on cone shaped disc 4 ultrasonically by means 
disposed at the upper end of funnel 3. 
A weighing station 13 is provided at the outer end of each of the secondary 
feed conveyors 5. One such weighing station is shown in each of FIGS. 2, 3 
and 4. As can be seen in FIG. 3, each weighing station is provided with an 
upper hopper 14 which receives product from the outer end of secondary 
feed conveyor 5. This hopper is operatively connected with an upper 
weighing head located within the cabinet 13. A hinged gate 15 is provided 
on the lower end of hopper 14 for delivery of product from hopper 14 into 
hopper 16. Hopper 16 is likewise connected with a weighing system disposed 
within cabinet 13 which is entirely independent of the weighing suspension 
for hopper 14. A hinged gate 17 is provided for delivery of product from 
hopper 16 into a delivery chute 18. 
In FIG. 4 the weighing station 13 is shown in its normal operative position 
with the hopper 14 disposed immediately below the outer end of the 
secondary feed conveyor 5. The weighing stations 13 are mounted so that 
they can be easily tilted back for easy access to the hoppers and related 
structure. 
It is to be noted that the chutes 18 which deliver product from the lower 
hoppers of the weighing stations are located around the periphery of a 
delivery tube 19 disposed immediately below the central platform 8. By 
tilting back or removing the weighing stations 13 access to the central 
delivery tube is facilitated for cleaning purposes and the like. 
Referring now to FIG. 1 there are shown three secondary conveyors and 
weighing stations in block form. There may be any number of weighing 
stations provided and in one embodiment ten such stations are provided, 
each station being identical and containing an upper weighing head, lower 
weighing head and local computer. The double lines show the flow of 
product from the secondary conveyor to the upper weighing head and from 
the upper weighing head to the lower weighing head from which the product 
is delivered to a package. The main computer provides instructions to each 
of the local computers so that the weight set for each upper weighing head 
is at a different fraction of the total desired package weight. For 
example, for a sixteen ounce desired final package weight, the first upper 
weighing head could be set for ten ounces, the second weighing head for 
eight ounces, the third weighing head for four ounces the fourth weighing 
head for two ounces, the fifth weighing head for one ounce, the sixth 
weighing head for one-half ounce, the seventh weighing head for 
one-quarter ounce, the eighth weighing head for one-eighth ounce, the 
ninth weighing head for one-sixteenth ounce and the tenth weighing head 
for one-thirtysecondth ounce. Product is delivered along the secondary 
conveyors and continues until the product delivered to the upper hopper in 
each weighing station reaches the predetermined fractional value of the 
desired final weight for which that weighing unit is set. At that point, 
the vibratory feeder for the secondary conveyor delivering product to that 
weighing unit is shut off and the product in the upper hopper is dumped 
into the lower hopper where the weight is checked. The checked weight is 
then fed back to the main computer and the main computer determines which 
particular combination of weights most accurately totals the desired final 
package weight. When that determination is made the product from the 
selected weighing stations is delivered to the central delivery tube and 
into the open package disposed at the lower end of the delivery tube. The 
cycle is then recommenced with only those weighing stations which 
delivered product for the preceeding package being refilled for the next 
succeeding package. 
The main computer determines the number of weighing stations which deliver 
product to make up the desired weight and if the number of such stations 
exceeds a predetermined number, for example, four, the computer will set 
up the weights measured by the upper weighing heads so as to reduce the 
number of stations required to make up the final package weight. In the 
event the number of weighing stations delivering product for a single 
package is less than a predetermined number, for example, four, then the 
computer will reduce the weight set for each upper weighing head so as to 
increase the number of weighing stations delivering product for a single 
package. By this means a method and apparatus is provided for obtaining 
exceedingly accurate package weights on a consistant basis. 
Obviously many modifications and variations of the present invention are 
possible in light of the above teachings.