Computerized Combination Weigher With Preset Optimum Weigher Discharge

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.

FIG. 1 is a block diagram showing the input and output signals to the main computer and to the computers located in each weighing station;

FIG. 2 is a perspective view of the feed conveyors to the individual weighing stations;

FIG. 3 is a perspective view of a weighing station tilted from its operative position, and

FIG. 4 is a perspective view of a weighing station and the delivery tube to deliver product to a package.

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.