Combination Weighing Machine Having Volume Confining Function

This invention relates to a combination weighing machine, especially, to such machine for delivering batches of articles each having a volume and weight greater than predetermined values.

When packing flaky articles such as cornflakes in bags, it is sometimes requested that the articles in each bag be above a predetermined value not only in their weight, but also in their volume. This is because such articles are fragile and, if crushed, are less in volume and lower in commercial value, even if their weight is acceptable. As disclosed, for example, in U.S. Pat. No. 3,939,928, the combination weighing machine is arranged to weigh articles by a plurality of weighing units at the same time and combine the resultant weight values in various fashion to select a combination the total weight of which satisfies a predetermined condition. However, the selected combination cannot be loaded with volume condition in general, even though it satisfies the weight condition. U.S. Pat. No. 4,388,975 discloses a special combination weighing machine which can cause at least one of a plurality of weighing units to participate always in the selected combination. This machine is designed always to mix some specific kind of articles in the selected combination. In such case as above, where the selected combination must have a volume greater than a predetermined value, the object can be attained by loading the weighing unit always participating in the selected combination with articles which have previously been measured out to have about a predetermined volume. In this case, however, if the articles having been measured out satisfy the weight condition by themselves, the object can be attained only by delivering these articles and there is no need to generate additional combinations, which would only be a waste of time.

Accordingly, an object of this invention is to provide a combination weighing machine which can weigh out articles having a volume above a predetermined value and satisfying a predetermined weight condition, without waste of time as above.

While the combination weighing machine according to this invention includes a plurality of weighing units each adapted for weighing articles to produce corresponding weight signals, means for effecting combination operation of the weight signals, means for comparing the resultant sum weights of combinations with a predetermined weight condition to decide whether they are acceptable or not, and means for unloading and loading those weighing units having participated in the accepted combination. As a feature of this invention, at least one of the plurality of weighing units always participates in the selected combination, as in the device disclosed in the above U.S. Pat. No. 4,388,975. Means is provided for comparing the weight signal from the weighing unit always participating with the above weight condition to decide its acceptability and, if acceptable, unloading and loading this weighing unit but, if unacceptable, actuating the above combination operation means, and comparing means.

Other objects and features of this invention will be described in more detail hereinunder with reference to the accompanying drawings.

In the drawings:

FIG. 1 is a partially sectional schematic side view representing a mechanical configuration of an embodiment of the combination weighing machine according to this invention;

FIG. 2 is a partially broken-away exploded perspective view representing a constant volume feeding device used in the embodiment of FIG. 1;

FIG. 3 is a block circuit diagram representing an electrical configuration of the embodiment of FIG. 1;

FIG. 4 is a block diagram representing a modification of a part of the circuit arrangement of FIG. 3;

FIG. 5 is a block diagram representing an electrical configuration of another embodiment of the combination weighing machine according to this invention; and

FIGS. 6, 7 and 8 are plan views illustrating another embodiment of the constant volume feeding device of FIG. 2.

Throughout the drawings, the same reference numerals are given to equivalent structural components.

Referring to FIG. 1, the combination weighing machine includes weighing units 10.sub.a, 10.sub.b, 10.sub.1, 10.sub.2, . . . 10.sub.i, . . . 10.sub.n arranged circularly on a frame 12 and provided with weighing hoppers 14.sub.a, 14.sub.b, 14.sub.1, 14.sub.2, . . . 14.sub.n and weight sensors 16.sub.a, 16.sub.b, 16.sub.1, 16.sub.2, . . . 16.sub.n, respectively. Two of these weighing units, 10.sub.a and 10.sub.b, are provided with weighing hoppers 14.sub.a and 14.sub.b, respectively, which are substantially greater in volume than those of the other units and, as described later, loaded with articles having a predetermined volume by a common constant volume feeding device 18. The articles are also fed from the feeding device 18 through a vibration conveyer 20 to the central portion of a conical distribution feeder 22, and further supplied through vibration conveyers 24.sub.1, . . . 24.sub.i, . . . 24.sub.n and holding hoppers 26.sub.1, . . . 26.sub.i , . . . 26.sub.n to the weighing hoppers 14.sub.1, . . . 14.sub.i, . . . 14.sub.n, respectively. A common collection chute 28 is located under the weighing hoppers 14 for collecting the articles discharged from the selected weighing units to deliver them to a packing machine (not shown). Supply of the articles to the constant volume feeding device 18 is effected by a feeding machine 30 provided with a crusher 32 to be described later.

As shown in detail in FIG. 2, the constant volume feeding device 18 includes a cylindrical tank 34 having a bottom plate 36 in which a pair of through-holes 38.sub.a and 38.sub.b are formed at 180.degree. interval. The holes 38.sub.a and 38.sub.b communicate with the weighing hoppers 14.sub.a and 14.sub.b, respectively, by tubular chutes 40.sub.a and 40.sub.b. On the bottom plate 36, there is a concentric thick volumetric disc or cylinder 42 having an even number (eight, in this embodiment) of cylindrical through-holes 44 which can register with the holes 38.sub.a and 38.sub.b of the bottom plate 36. The volumetric disc 42 is designed such that the volume of each hole 44 is equal to one half of the lower threshold of the abovementioned predetermined volume of articles. On the volumetric disc 42, there is a top plate 46 having a pair of through-holes 48.sub.a and 48.sub.b which are similar to the holes 38.sub.a and 38.sub.b of the bottom plate 36 but angularly displaced therefrom by about 90.degree.. The bottom and top plates 36 and 46 are fixed to the tank 34, while the volumetric disc 42 can move slidingly between the both plates. The volumetric disc 42 is fixed at its center to a shaft 50 and a pulley 52 fixed to the lower end of the shaft 50 is coupled through a belt 54 to a pulley 58 of a motor 56 (see, FIG. 1). The motor 56 includes a suitable reduction gear device and rotates the volumetric disc 42 by one pitch (the angle between the adjoining holes 44) in response to a driving signal which will be described later. A conical cap 60 having four vanes 62 is fixed to the top of the shaft 50 for rotating with the disc 42 to stir the articles in the tank 34 for preventing retardation. The side wall of the tank 34 has an exit port 64 just above the top plate 46, which opens just above the vibration conveyer trough 20. Accordingly, when the shaft 50 is driven in such a state that a suitable amount of articles have been fed in the tank 34 from the feeder 30, the vanes 62 rotate with the volumetric disc 42 to stir the articles in the tank 34 and the articles fall in the volumetric holes 44 when they register with the holes 48.sub.a and 48.sub.b of the top plate 46 and then fall in the weighing hoppers 14.sub.a and 14.sub.b through the chutes 40.sub.a and 40.sub.b when the holes 44 register with the holes 38.sub.a and 38.sub.b of the bottom plate 36. At the same time, the articles in the tank 34 stirred by the vanes 62 fall down onto the conveyer trough 20 from the exit port 64 by gravity and are successively conveyed to the dispersion feeder 22.

Referring to FIG. 3, weight signals generated by the weight sensors 16.sub.a and 16.sub.b of the weighing units 10.sub.a and 10.sub.b are summed by an adder 66 and the resultant sum is applied to a comparator 68. On the other hand, weight signals generated by the weight sensors 16.sub.1, 16.sub.2, . . . 16.sub.n of the weighing units 10.sub.1, 10.sub.2, . . . 10.sub.n are selectively summed by a selective adder circuit 70 controlled by combination control signals generated by a combination generator 72 and the resultant sum weights are successively supplied to a judge circuit 74. The combination generator 72 has outputs 1, 2, . . . n corresponding to the weight sensors 16.sub.1, 16.sub.2, . . . 16.sub.n, which are coupled also to corresponding inputs of a combination memory 76. In addition to these inputs, the combination memory 76 has a further input terminal 0 which is always provided with a logic high level signal from a suitable source (not shown). The comparator 68 compares the sum weight from the adder 66 with a lower threshold weight (the allowable lower limit of the combined weight) preset in a lower threshold weight register 78 and, when the former is greater than the latter, produces a logic high level signal which is applied through an OR gate 82 to unloading devices 84.sub.a and 84.sub.b for the weighing hoppers 14.sub.a and 14.sub.b. The unloading device is an electromechanical device which responds to the high level signal to open the gate of the corresponding weighing hopper for a predetermined time to discharge its content and may be of any configuration known to those skilled in the art. The high level signal is also applied through the OR gate 82 and a delay element 86.sub.0 to a loading device 88.sub.0. The loading device 88.sub.0 includes the motor 56 of the constant volume feeding device 18 and, as described previously, responds to the input signal to rotate the volumetric disc 42 by one pitch to supply new articles which have been measured out by volume to the unloaded weighing hoppers 14.sub.a and 14.sub.b. The delay element 86.sub.0 is used for setting a time difference between the unloading and loading operations and may be of any type known to those skilled in the art.

When the sum weight from the adder 66 is less than the lower threshold weight, the comparator 68 provides a logic low level signal through an invertor 90 to the combination generator 72 as its start signal. In response thereto, the combination generator 72 initiates its operation and supplies its output signals to the selective adder circuit 70. Thus, the selective adder circuit 70 also initiates arithmetic operation under control of the output signals of the combination generator 72. In addition to the weight signals from the weight sensors 16.sub.1, 16.sub.2, . . . 16.sub.n, the sum weight from the adder 66 is also applied to the selective adder circuit 70 so that this input from the adder 66 participates always in any combination regardless of the output format of the combination generator 72. This circuit arrangement is described in detail in the above U.S. Pat. No. 4,388,975 and will not be described further. The combined sum outputs of the selective adder circuit 70 are compared with the lower threshold weight preset in the lower threshold weight register 78 and with an upper threshold weight preset in an upper threshold weight register 80 in the judge circuit 74 which provides an acceptance signal to the combination memory 76 when any combined sum falls between the thresholds. The combination memory 76 stores the current input format and also supplies corresponding output signals directly to the unloading devices 84.sub.1, . . . 84.sub.n, and through delay elements 86.sub.1, . . . 86.sub.n to loading devices 88.sub.1, . . . 88.sub.n. These unloading devices, delay elements and loading devices operate similarly to the abovementioned 84.sub.a, 84.sub.b, 86.sub.0 and 88.sub.0 and respond to logic high level input signals to unload and load the corresponding weighing units. In this case, the weighing units 10.sub.a and 10.sub.b are also unloaded and loaded together as described previously, since a high level output signal is applied then to the OR gate 82 from the output terminal 0 of the combination generator 72.

Thus, each batch of articles collected in the collection chute of FIG. 1 and then delivered to the packing machine is rendered to have a volume equal to or greater than the specified value and a weight within the specified range.

Although, in the above embodiment, two weighing units (10.sub.a and 10.sub.b) were shown to be fed from the constant volume feeding device 18, this is only for illustrative purpose and has no special significance. A single constant volume weighing unit may be used and it may be rather economical since the adder 66 can be omitted. However, it is also true that the more the constant volume weighing units, the less the volumetric error. The volumetric error may be caused by insufficient filling of the volumetric holes 44 of the volumetric disc 42. In order to avoid it, the holes 48.sub.a and 48.sub.b of the top plate 46 may be substituted with arcuate slots 49.sub.a and 49.sub.b which can cover a plurality of holes 44, respectively, as shown in FIG. 6. Although, in the above embodiment, the combined weight was assumed to be allowable if it fell within the predetermined range, it is also possible to select out such a combined weight which is equal or nearest to the lower threshold weight. The configuration of the judge circuit 74 for this purpose is disclosed, for example, in U.S. Pat. No. 4,416,341 or U.K. Pat. No. 2,089,153. In general, the target weight condition can be predetermined arbitrarily by designing the comparator 68, judge circuit 74 and their associated circuits so as to meet the requirement and all devices including such modified circuit arrangement are also within the scope of this invention.

When the shape and/or size of the articles are indefinite, a large variance may be anticipated in the weight of each batch delivered from the constant volume feeding device 18. When the weight of each batch is too small (that is, the apparent specific gravity is too small), a greater amount of articles will be added during the combination weighing operation and this may prevent normal prescribed packing from being effected by the associated packing machine. In order to avoid this problem, the feeding machine 30 of FIG. 1 is provided with a crusher 32 for crushing the articles adequately to increase the apparent specific gravity thereof. In order to control this crusher 32 automatically, the arrangement of FIG. 3 also includes a crusher control device comprising a subtracter 92 receiving the outputs of adder 66 and upper threshold weight register 78, a deviation register 94 for storing a predetermined weight deviation threshold, a second subtracter 96 receiving the outputs of deviation register 94 and subtacter 92, and a control circuit 98 receiving the output of subtracter 96. As will be understood, subtracter 92 calculates every cycle the deviation of the weight of the predetermined volume of articles from the lower threshold weight and subtracter 96 calculates the deviation of the above-calculated deviation from the predetermined threshold deviation. The control circuit 98 responds to this deviation from the threshold deviation to provide an adequate control signal for controlling the operation time and/or energy of the crusher 32, depending upon its structure.

Another embodiment of crusher control device is shown in FIG. 4. This device includes a volume register 102 for storing the total volume of the articles fed to the constant volume weighing units, a divider 104 for dividing the weight output of the adder 66 by the content of volume register 102 to obtain the apparent specific gravity, an RASG register 108 for storing a predetermined reference apparent specific gravity (RASG), a subtracter 110 for calculating the deviation of apparent specific gravity from the stored RASG, and a control circuit 112 for responding to this deviation to control the crusher 32. The above RASG is equal to the quotient of the content of lower threshold weight register 78 divided by the content of volume register 102.

U.S. Pat. No. 4,385,671 and its continuation application Ser. No. 443,959 filed Nov. 23, 1982, or U.K. Pat. No. 2,077,067 discloses a combination weighing machine of so-called "double-shift" type which operates such that, before the weighing units having participated in a specific combination and then been unloaded and loaded reach their stable states, respectively, the next combination is selected from the remaining weighing units, thereby improving working efficiency of the machine. Now, the description will be made about another embodiment in which this invention is applied to this type of combination weighing machine, with reference to FIG. 5.

The circuit configuration of FIG. 5 is similar to that of FIG. 3, except that an inhibit circuit 114 is coupled between combination generator 72 and selective adder circuit 70 (and combination memory 76). The inhibit circuit 114 receives the weight signals from weight sensors 16.sub.1, 16.sub.2, . . . 16.sub.n to sense loading of specific weighing units from the values thereof and serves to inhibit high level signals from appearing at the corresponding outputs of the combination generator 72 for a predetermined time so that these weighing units do not participate in any combination until they become stable. Accordingly, before stabilization of the weighing units having participated in a combination and having unloaded and loaded again, the next combination operation can be initiated with the remaining weighing units. The inhibit circuit 114 may be actuated in response to the input signals of unloading devices 84.sub.1, . . . 84.sub.n or loading devices 88.sub.1, . . . 88.sub.n instead of the weight signals from sensors 16.sub.1, . . . 16.sub.n. Detailed configuration and operation of inhibit circuit 114 will not be described further, since they are described in the abovementioned U.S. or U.K. patent specification.

Further, in this embodiment, a single-pole, double-throw switch 116 is disposed in place of adder 66 of FIG. 1 and its fixed contacts a and b are coupled to the outputs of weight sensors 16.sub.a and 16.sub.b, respectively. The movable contact c of the switch 116 is coupled to one input of comparator 68 and to the "0" input of selective adder circuit 70. The output of comparator 68 is coupled to the movable contact c of a second single-pole, double-throw switch 118, whose fixed contacts a and b are coupled through OR gates 82.sub.a and 82.sub.b, respectively, to unloading devices 84.sub.a and 84.sub.b, and whose movable contact c is coupled through an OR gate 82.sub.c and delay element 86.sub.0 to loading device 88.sub.0. This high level output terminal 0 of memory 76 is coupled to the movable contact c of a third single-pole, double-throw switch 120 and to the other input of OR gate 82.sub.c, and the fixed contacts a and b of the switch 120 are coupled respectively to the other inputs of OR gates 82.sub.a and 82.sub.b. The three single-pole, double-throw switches 116, 118 and 120 are thrown concurrently in gang fashion in response to the output signal of delay element 86.sub.0 (or the input signal of loading device 88.sub.0), in such fashion that, when the contact a of switch 116 is in use, the contacts a of switches 118 and 120 are also in use.

Assuming now that all switches are in their contacts a, it should be understood the circuit arrangement of FIG. 5 operates similarly to that of FIG. 3, using only constant volume weighing unit 10.sub.a (without use of constant volume weighing unit 10.sub.b). In this condition, if loading of those weighing units which participated in the preceeding combination (including weighing unit 10.sub.a) is initiated, the input signal of loading device 88.sub.0 throws switches 116, 118 and 120 to their contacts b at the same time. This results in removal of weighing unit 10.sub.a from the next combination and, in co-operation with the abovementioned inhibit circuit 114, the next combination operation can be started immediately with the remaining weighing units which did not participate in the combination. While all switches will return to their contacts a upon completion of the next combination operation, the weighing unit 10.sub.a will be in its stable state already and be able to participate in the combination after next.

In the arrangement of FIG. 5, in contrast to that of FIG. 3, constant volume weighing units 10.sub.a and 10.sub.b must be loaded alternately since they are used alternately. This can be done, as shown in FIG. 7 (a plan view of constant volume feeding device 18 from which top plate 46 and overlying components are removed) by making the number of volumetric holes 44 of volumetric disc 42 odd so that the volumetric holes register alternately with holes 38.sub.a and 38.sub.b of bottom plate 36. The above-described constant volume feeding device 18 was given only for illustrative purpose and any other type of constant volume feeding device can be used for the device of this invention.