US3342225A

US3342225A - Automatic feed control system

Info

Publication number: US3342225A
Application number: US506559A
Authority: US
Inventors: Stewart B Blodgett
Original assignee: MIRAPAK Inc
Current assignee: MIRA-PAK MACHINERY Co Inc; ESAB AB; MIRAPAK Inc
Priority date: 1965-11-05
Filing date: 1965-11-05
Publication date: 1967-09-19
Anticipated expiration: 1984-09-19
Also published as: GB1112740A

Description

Sept. 19, 1967 s. a. BLODGETT AUTOMATIC FEED CONTROL SYSTEM Fil-ed Nov. 5, 1965 4 Sheets-Sheet L51 INVENT OR STEWART B. BLODGETI' Sept. 19, 1967 s. B. BLODG ETT 3,342,225

AUTOMATIC FEED CONTROL SYSTEM Filed Nov. 1965 4 Sheets-Sheet 1 FIG. 3-

INVENTOR STEWART B. BLODGETT ATTORNEYS p 9, 1967 s. B. BLODGETT 3,342,225

AUTOMATIC FEED CONTROL SYSTEM Filed Nov. 5, 1965 4 Sheets-Sheet 4 FIG. 4

INVENTOR STEWART B- BLODGETT ATTOR N BY 5 United States Patent 3,342,225 AUTOMATIC FEED CONTROL SYSTEM Stewart B. Blodgett, Houston, Tex., assignor to Mirapak Incorporated, Houston, Tex. Filed Nov. 5, 1965, Ser. No. 506,559 18 Claims. (Cl. 141--1) ABSTRACT OF THE DISCLOSURE Method and apparatus for controlling the actual feed rate of a product from a cyclically operable feeding apparatus to a packaging machine or the like. A differential mechanism receiving a first signal representing actual feed time and a second signal representing a predetermined feeding time and generating a third signal proportional to the difference between the first and second signals. Two mechanisms are shown for responding to the third signal to vary the actual feeding rate. In one mechanism the third signal changes the amplitude of the vibrations of the vibrating feeder; and in the other mechanism the third signal changes the weight of product present on the vibratin g feeder.

This invention relates to a method and apparatus for regulating the feeding rate of a product from a feeding apparatus to a machine adapted to receive the product. In particular the invention relates'to a method and apparatus for regulating the rate of feed of a bulk product such as potato chips, hard candies, cereals, coffee, etc., in predetermined weighted charges to a packaging machine adapted to receive each weighted charge for packaging the same, wherein the actual feeding rate of the product feeding apparatus is regulated and made to approach the available feeding rate of the packaging machine cycle.

The present invention may be employed with a product feeding apparatus which delivers a weighted charge of product to a dump bucket where the charge is weighed and stored and from which the charge is dumped into a unit package carried by a cyclically operable packaging machine.

Continuous monitoring and regulation of the feed rate is desirable because several factors can cause changes in the feed rate of many products while the feeding machine is running. The bulk density of the product can change, changes in surface finish of the product can affectthe speed at which the product will move through the feeder, voltage variations can occur and accumulated product particles can adhere to the feeder pans thereby slowing the movement. It is the purpose of this invention to pro vide a method and apparatus for continuously sensing the feed rate of product and to adjust when necessary to maintain optimum feed time in relation to the speed of the packaging machine. Adjustments are also automatically made if the speed of the packaging machine is changed.

The packaging machine may be similar to that disclosed in US. Patent 3,027,696 to Leasure, issued on Apr. 3, 1962. In the Leasure packaging machine a strip of packaging material is formed into a vertical cylindrical tube having an open upper end positioned immediately below the dump bucket of the product feeding apparatus and movable downwardly away from the feeding apparatus. A pair of movable jaws on the packaging machine move horizontally into contact with the tube to form a first seal across the vertical tube. The jaws, while in con- 3,342,225 Patented Sept. 19, 1967 mains open long enough to deliver the product, then closes after the sealing jaws have moved downwardly with the tube a certain distance, then separate from the tube and ride upwardly back to the horizontal level where they first contacted the tube. The jaws are now ready to form a second, or upper seal across the tube. If the predetermined weight of product has accumulated in the dump bucket to fill the next bag the jaws will again come into contact with the tube forming a second or upper seal in a manner identical to that by which the first, or lower seal was formed. When the second or upper seal reaches the lower position the tube is cut across the second seal to form a unit package of product in the tube between the first and second seals. The portion of the second or upper seal above the cut then serves as the first, or bottom seal for the next package to be formed, and so on. If for some reason sufiicient product has not accumulated in the dump bucket at the moment that the sealing jaws are ready to move inwardly to form the second or upper seal (ready position. of the jaws), the jaws will not move in; but rather, they will go through an idle cycle during which they will not touch the tube, and then will return to the ready position to move inwardly to form the second seal. Idle cycles will be continued until the jaws are in the ready position and the dump bucket contains the predetermined weighted charge of product.

It can be seen that the packaging machine cycle is such that it will allow product to be fed from the feeding apparatus to the dump bucket only during a certain portion of the packaging machine cycle. This portion of the packaging machine cycle will be referred to as available feed time. In the cycle of the packaging machine shown in the Leasure patent, available feed time occurs between (1) the point when the dump bucket gate closes after delivering a charge of product and (2) the ready position at which the sealing jaws require a full dump bucket signal before they move inwardly to form an upper, or second seal.

Although the actual feed time will normally be compared to the available feed time of the packaging machine, as defined above, it is within the scope of the invention to compare the actual feed time to a timing means which is completely independent of the operation of the packaging machine. In this manner the speed of the feeding apparatus in terms of packages per minute can be selected independently of the packaging machine.

It has been known heretofore to feed a predetermined Weighted charge of bulk product from a feeding apparatus to a dump bucket for weighing and storage and then delivering the charge from the bucket to a packaging machine. Further, it has previously been recognized that optimum conditions are attained as long as the time required for the feeding apparatus to deliver a weighed charge of product to the dump bucket matches the speed of the packaging machine.

However, in the previous feeding apparatus and packaging machines no attempt was made to continuously or automatically regulate the actual feeding rate. The operating level of the feed motor of the feeding apparatus was set initially so that it would feed a weighted charge of product of average characteristics to the dump bucket in the time made available by the packaging machine. However, with no further control the actual feeding time necessary to deliver the desired weight of product to the dump bucket became very large or very small in relation to the amount of available feed time of the packaging machine. Disadvantages were presented by either too large or too small an actual feed time. If the actual feed time is to great (the actual feed rate too small) then the packaging machine will go through many cycles in which no bag is filled since at the crucial moment when the packaging machine signals for the dump bucket gate to open and deliver a charge of product, the product feeding anparatus will not have delivered a full load of product to the dump bucket. Accordingly, too long an actual feed time renders the entire operation uneconomical since (1) less filled packaged bags will be formed and (2) the packaging machine will undergo much useless motion by going through idle cycles without forming bags.

Similarly, an actual feeding time far shorter than the available feed time of the packaging machine (a greater feeding rate then is necessary) is equally undesirable since a greater actual feeding rate will substantially reduce overall accuracy. The greater actual feeding rate may be caused by voltage variations in the feeding apparatus, increased product density, or by many other factors. Also, where the greater actual feed rate is experienced, scale lead will have to be quite high to account for the large amount of product in the air on the way to the dump bucket at the moment that the feeding apparatus is cut off. The greater the required scale lead, the less will be the overall accuracy.

The best possible operating condition of the feeding apparatus would be obtained when the apparatus feeds the thinnest possible bed of product so as to use as much available feed time as the packaging machine permits without exceeding that available feed time. Under these conditions the best possible weighing accuracy and economy of operation is obtained. The greater accuracy is obtained because scale lead is at a minimum. It is also desirable that these conditions be kept constant because the greatest weighing accuracy will result when the scale lead is constant. Economy of operation is obtained because wasted, or idle packaging machine cycles are held to a minimum. Without the present invention it was impossible to maintain this optimum actual feeding rate adjustment for any length of time. Following an initial feed time setting the product feeding apparatus would then slow down or speed up as a result of which the above discussed disadvantages would be evident.

The present invention overcomes these disadvantages of the prior art by providing a feed control for the product feeding apparatus which automatically and continuously adjusts the actual feed rate to match the speed of the packaging machine and thereby utilize as much as possible of the available feed time permitted by the packaging machine.

According to the present invention a differential mechanism receives a first signal from a product feeding apparatus indicating the actual feed time required for the apparatus to supply the predetermined weighted charge of product to the dump bucket. A second signal is set into the differential mechanism indicating the available feed time of the packaging machine; that is, the period of time of the total cycle time of the packaging machine during which feeding of product to the dump bucket may occur. Alternatively the second signal may indicate a standard, or predetermined time transmitted to the differential mechanism from a common timing mechanism. These two signals are then compared in the differential mechanism and their difference is transmitted back to the product feeding apparatus. At the product feeding apparatus a mechanism is provided which is responsive to the output signal from the differential to change the actual feeding rate of the product feeding apparatus so that actual feed time approaches the available feed time permitted by the packaging machine cycle.

The possible arrangements for causing the differential output signal to effect a change in the actual feeding rate of the product feeding apparatus are of course infinite. In the present application I have disclosed two possible arrangements for obtaining this result.

In a first application of the invention the output signal from the differential varies the rheostat setting of the motor which vibrates feeder pans of the feeding apparatus. This in turn controls the amplitude of the vibrators. The greater the amplitude of the vibrations the greater will be the actual product feed rate. Thus by increasing or decreasing the amplitude of vibrations of the feeder pans of the feeding apparatus the actual feed rate may be increased or decreased respectively.

In a second application of the invention a feeding apparatus is employed wherein a vibrating supply hopper is interposed between a product conveyor and the vibrating feeder pans. The supply hopper starts and stops in synchronism with the feeder pans. In this apparatus the weight of product on the supply hopper is measured by a hopper cell or scale. This scale in turn controls the movement of the product conveyor in transporting product to the supply hopper. By means of a hopper cell control unit the weight of product on the supply hopper below which the product conveyor is caused to transport more product to the supply hopper is set into the hopper cell or scale. This weight setting of the hopper cell (that is, the weight below which it calls for more product to be delivered from the product conveyor) is increased or decreased in accordance with the output signal from the differential. For example, if the differential output signal indicates that the time required for the feeding apparatus to feed the predetermined weight of product is much shorter than the available feed time of the packaging machine (that is, too great an actual feeding rate) then the hopper cell control unit reacts to require less product from the product conveyor. It does this by decreasing the weight level of product on the supply hopper below which the hopper cell will signal for more product to be delivered from the product conveyor. Alternatively, if the output signal from the differential indicates that the feeding time is too great (too slow a feeding rate), then the weight setting below which the hopper cell calls for more product to be delivered from the product conveyor to the supply hopper will be increased, causing a greater weight of product to be fed from the product conveyor to the supply hopper.

Accordingly, it is an object of this invention to provide a method and apparatus for controlling the actual feeding rate of a feeding apparatus which overcomes those disadvantages present in the previous devices by providing optimization of the feeding rate.

It is another object of this invention to provide a method and apparatus for controlling the actual feeding rate of a product feeding apparatus by continuously and automatically adjusting the actual feed time so that it approaches the available feed time permitted by the packaging machine.

It is another object of this invention to provide a method and apparatus for controlling the actual feeding rate of a product feeding apparatus by continuously and automatically adjusting the actual feed time so that it approaches a predetermined feed time.

It is still another object of this invention to control the feed rate of a product feeding apparatus by adjusting the amplitude of the vibrations of the feeding apparatus.

Another object of this invention is to control the actual feed rate of a product feeding apparatus by controlling the setting at which the feeding apparatus causes more product to be fed thereto from the product storage.

It is still another object of this invention to provide a visible indication of the setting required to maintain the desired feeding rate of the product feeding apparatus at any given moment.

Other objects and many of the intended advantages of the present invention will become more fully apparent upon consideration of the following detailed specification in connection with the accompanying drawings wherein:

FIG. 1 is a schematic drawing illustrating the basic operation of the invention.

FIG. 2 is a partial schematic drawing illustrating the differential mechanism of the invention.

FIG. 3 shows a product feeding apparatus illustrating one application of the invention.

FIG. 4 shows a product feeding apparatus illustrating a second application of the invention.

FIG. 5 shows the mechanism which operates the product conveyor shown in FIG. 4.

FIG. 1 illustrates schematically the basic operation of the invention as applied to a product feeding apparatus and a packaging machine. The product feeding apparatus receives a continuous stream of product articles such as potato chips, pretzels, hard candies, cereals, coffee or the like in bulk form and delivers the same in charges of a predetermined weight to a packaging machine wherein bags or other packaging units are positioned to receive the weighted charges of product.

A differential mechanism 13 is designed to receive a signal 14 from the product feeding apparatus indicating the actual feed time required to feed the predetermined weighted charge of product and a signal 15 from packaging machine 11 through a cam and microswitch 16 indicating the available feed time permitted during the packaging machine cycle. The differential mechanism then compares the actual feeding time with the available feed time, determines the difference therebetween, and transmits a signal 17 to the product feeding apparatus to correct the feeding rate so that the actual feeding time approaches the available feeding time permitted by the packaging machine.

FIG. 2 illustrates the differential mechanism employed in the present invention. The basic purpose of the differential mechanism 13, as discussed above, is to compare the actual feed time and the available feed time and transmit a signal of the difference therebetween back to the product feeding apparatus to correct the actual feeding rate.

This comparison of actual and available feed time is accomplished by employing two

synchronous motor units

21 and 25 each equipped with a clutch and brake unit for controlling the engagement of each synchronous motor within the differential mechanism. The synchronous m0- tors run the entire time that the machine is in operation. However the output shafts from the motors (thus the inputs to the differential mechanism) turn only when the clutch mechanism is energized and the brake disengaged. The synchronous motor unit 21 is mounted to receive a signal representing actual feed time and to transmit the same to the differential. The motor 22 turns continuously, but the output shaft 30 and gear 30' turn only when the clutch 23 is energized and the brake 24 disengaged. Referring to FIG. 3 the scale 67 weighs the product delivered to the pump bucket 72 which holds the product for subsequent delivery to the packaging machine. Signal 69 continuously feeds to control relay 62 a signal representing the actual weight of product in dump bucket 72. When the predetermined weight is reached in the scale 67 the control relay 62 cuts off the feeding apparatus. A signal 69' is transmitted from the control relay 62 to the clutch mechanism 23 and the brake 24 of the synchronous motor unit 21 to energize the clutch and disengage the brake whenever the feeder pan is vibrating. In this manner the output shaft 30 and gear 30 rotate whenever the feeding apparatus is feeding product to the dump bucket 72. The brake 24 stops the rotation of output shaft 30 and gear 30' immediately upon de-energization of the clutch mechanism 23. In this manner the rotation of the gear 30 accurately indicates the actual time required by the product feeding apparatus to feed a predetermined weighted charge of product to the dump bucket 72.

The available feed time permitted by the packaging machine cycle is transmitted to the camshaft synchronous motor 25. The motor 26 rotates continuously but the output shaft 39 and gear 39 rotate only when the clutch 27 is energized and the brake 29 is disengaged. Energization of the clutch 27 is controlled by current passing through a microswitch 16. The microswitch 1-6 is in turn controlled by a cam 16' which is mounted on and thereby turns with the shaft of the packaging machine. The raised portion of cam 16' will close microswitch 16 and thereby energize clutch 27 and disengage brake 29. The raised portion of 6 the circumference of cam 16 corresponds to the portion of the packaging machine cycle which is available feed time; that is, the portion of the packaging machine cycle during which the packaging machine permits the feeding apparatus to feed product to the dump bucket. For instance in the Leasure type packaging machine referred to above, the raised portion of cam 16' would correspond to the portion of the packaging machine cycle between gate close and ready position. In this manner, available feed time is fed into the differential.

Although the preferred embodiment of this invention, as described above, employs a cam operated microswitch to control the energization of clutch 27, it is also within the scope of the invention to employ other means to cause selective engagement of clutch 27. For instance a periodic pulse signal may be transmitted directly to the clutch to cause engagement and disengagement thereof; and the frequency of this pulse may be responsive to the operation of the packaging machine or to a timing means independent of the packaging machine such as another feeding apparatus or a standard timing mechanism. As another example, the microswitch and cam may be replaced with a stepping switch which causes periodic engagement of clutch 27.

At this point, two signals have been set into the differential 13, the first representing the actual feed time of the product feeding apparatus and the second representing the available feed time permitted by the packaging machine. These signals are the amount of rotation of gears 30 and 39' respectively. If one gear turns exactly the same amount as the other the actual feed is in perfect adjustment. If however the actual feed time is too long the gear 30 will turn more than the gear 39' because the feeding apparatus has been running longer than it should for the scale 67 to reach the predetermined weight.

The two gears 30' and 39' are connected to thedifierential 13 in order to make an accurate comparison of the shaft rotations and to cause an adjustment to be transmitted back to the product feeding apparatus if it is not perfectly adjusted. Two bevel gears 32 and 41 are freely rotatably mounted on the differential output shaft 37. Gear 32 is rigidly connected to gear 31 which is turned by gear 30 when the clutch 23 is energized. Similarly, gear 41 is rigidly attached to gear 40 which is turned by gear 39 whenever clutch 27 is energized. The two gears 30" and 39' are driven in opposite directions by their

respective motors

22 and 26. Thus if each of the two gears 30' and 39 were turned the same amount then the gears 32 and 41 would also turn in opposite directions by the same amount. As a result the bevel gear 34, mounted between and engaging gears 32 and 41 would merely rotate about its axis. However, if gear 32 were turned while gear 41 did not turn then the gear 34 would still be forced to rotate by gear 32 and in doing so would roll around on gear 41. A stub shaft 35 is freely rotatably mounted in bevel gear 34 but is rigidly attached to the differential output shaft 37. As gear 34 rolls around either bevel gear 32 on 41 it causes the stub shaft 35 to turn the differential output shaft 37. The turning of the shaft 37 is the mechanical output signal of the differential 13. This mechanical output signal generates an electrical signal 43 in generator 42 and signal 43 is transmitted to the product feeding apparatus to change the actual feeding rate. The nature of the signal 43, which will depend on the particular type of product feeding apparatus being used, will be discussed in more detail below. For the present, in one type of feeding apparatus the generator is a rheostat which varies the signal 43 controlling the amplitude of vibrations of the feeder pan 57 (see FIG. 3), and in a second type of feeding apparatus the signal controls the setting of a hopper scale which will in turn control the quantity of product fed from product storage to the feeder pans (see FIG. 4).

In summary, any change in the speed of the packaging machine will cause a change in the amount of rotation of the gear 39 and this will in turn cause the output shaft of the differential to transmit a signal to the product feeding apparatus to adjust the actual feeding time accordingly. Also, any change in the actual feeding time (such as might be caused by product build-up on the pan, voltage variations, change in chip size, etc.) will be transmitted to the differential 13 by the gear 30' and a correction signal will be transmitted back to the product feeding apparatus.

Although it is possible to adjust for the smallest variation between the actual product feeding time and available feeding time, package to package variations are disregarded because of built-in backlash in the geared couplings of the differential mechanism. In this way adjustments are made only for consistent variation, no matter how small, because their effect is cumulative. That is, if the product feeding apparatus runs the smallest fraction of a second too long, on the average, the differential mech anism will move to effect a correction.

FIG. 3 shows one application of the invention to a product feeding apparatus. Referring to FIG. 3 the product chute 50 temporarily stores the product until it is carried away by the product conveyor 51. An important function of the product chute is to provide a head of product that will slide onto the product conveyor. An upper, or rake-off switch 52 and a lower or interlock switch 53 are provided on the chute 50. The upper switch 52 signals for a supply of more product while the lower signal switch '53 stops the machines feeder pan 57 if the product supply is too low. The feeder pan 57 does not stop however until the predetermined weight is fed to the dump bucket 72. It is important that enough reserve is left in the product chute when the interlock switch 53 operates to complete the cycle without leaving a gap in the bed of product on the product conveyor.

The product conveyor 51 carries the product from chute 50 and delivers the product to the feeder pan 57. The product conveyor is operated intermittently by a piston in a double acting air cylinder (not shown), the feed stroke of which is cut ofi by switch 54 in the feeder pan 57 when a sufficient supply of product has been fed from the conveyor 51 to the pan 57, or the stroke is cut off by a pressure switch (not shown) if the piston reaches the end of its stroke without the air cylinder being cut off by switch 54. Switch 54 in the feeder pan, acts to control the piston through a solenoid coil and a solenoid valve. The full stroke cut-off pressure switch is operated by the air cylinder which moves the conveyor. This full stroke cutoff cylinder moves the conveyor. This full stroke cut-off pressure switch is provided with a needle valve to provide a time delay which controls the movement of the piston in the double acting air cylinder.

The conveyor speed should be adjusted to move slowly enough so that the switch 54 stops the conveyor before it reaches the end of its travel. The conveyor pressure switch should seldom if ever operate. Its purpose is to return the conveyor air cylinder in case one full stroke does not deliver enough product.

As product enters the feeder pan 57 it piles up on the slope at the back of the feeder pan to provide a small head of product to assure a uniform bed of product at the front of the feeder pan. The feeder pan delivers product to the dump bucket 72. Movement of product along feeder pan 57 is imparted by a conventional vibrating mechanism 60. The amplitude of the vibrations of the vibrator determines the rate at which the product will be fed to the dump bucket 72. The greater the amplitude, the greater will be the product feed rate. The amplitude of vibration is in turn controlled by the voltage fed to the vibrator 60 along line 63 and this is in turn controlled by a rheostat 64. The feeder pan vibrator operates at one level, until a preset weight level is reached and control relay 62 cuts off signal 69 thereby stopping the vibrator 60 and deenergizing the clutch and engaging the brake in motor unit 21. Weight control knob, 66, located on the control relay 62 determines the weight at which the vibration of the feeding pan is cut off.

While the vibrator is operating to feed product to the dump bucket 72, a signal is transmitted from the control relay -62 to the feeder motor 21 of the differential 13 to indicate the actual feed time required to feed the predetermined weight of product to the dump bucket 72.

In a manner discussed above with respect to FIG. 2 the available feed time permitted by the packaging machine cycle is also being fed to the differential 13.

A mechanical signal 65, which is actually the angular position of the differential mechanism output shaft 37, indicating the difference between actual feed time and available feed time is then transmitted to the rheostat 64 to change the voltage transmitted to the vibrating device 60 of the feeder pan 57. This in turn changes the amplitude of the vibrations and the rate at which the feeding apparatus will feed a predetermined weight of product to the dump bucket 72.

The angular position of the differential output shaft 37 (and thus the setting of rheostat 64) is also transmitted to a feed control indicator 74. This signal is represented by line 77 in FIG. 3. A knob 74' moves along a scale indicating the vibrator rheostat setting and thereby indicating the actual product feeding rate. If the knob 74' moves toward the full clockwise position it indicates that the time to reach the predetermined weight is too high, or that the actual feed rate is too low, and that the amplitude of the feeder vibrator should be increased. The need for increasing the actual feed rate will be sensed by differential 13 in the manner discussed above and the signal will then be transmitted to the vibrator rheostat to increase the amplitude of the vibrations. Similarly, if the knob 74 moves toward the full counterclockwise position it indicates that the actual feeding time is too fast and that the vibration rheostat setting should be decreased to increase the time necessary for the predetermined weight of charge to be fed to the dump bucket 72. When the proper setting on the vibrator rheostat is achieved the feed control indicator will operate in the range between the full counterclockwise and the full clockwise position.

FIG. 4 illustrates another application of the invention to a second type of product feeding apparatus. In the feeding device shown in FIG. 4 a product chute 80 having a rake-off switch 52 and an interlock switch 53' is similar in construction and in purpose to the product chute of the feeding apparatus shown in FIG. 3.

The product conveyor 81 is similar in construction to the product conveyor 51 shown in FIG. 3 but its stroke is regulated in a manner different from that of the conveyor shown in FIG. 3.

Here the product conveyor delivers the product onto a supply hopper 82 rather than directly into the feeder pan. The weight of the product on the supply hopper 82 is measured by a hopper cell or scale 83. When the weight of product on the supply hopper falls below a certain level the deficiency is sensed by scale 83 and a signal is transmitted to the product conveyor to deliver more product to the supply hopper. A hopper cell control unit 84 determines the weight level below which the hopper cell 83 will call for more product to be delivered to the supply hopper 82. The actual rate of feed of the feeding apparatus depends upon the amount of product delivered to the feeder pan, and this in turn depends upon the weight of product on the supply hopper. Thus by changing the setting on the control unit 84 one controls the actual product feeding rate of the feeding apparatus.

In the feeding apparatus of FIG. 4 it is the control unit 84 rather than the feeder pan rheostat that is affected by the output signal from the differential mechanism. When the actual feed time is too great (too slow a feeding rate) the differential output signal 73, which is a measure of the angular position of differential shaft 37, is transmitted to the control unit 84 causing the unit 84 to increase the weight level below which cell 83 calls for more product 9 to be delivered from conveyor 81 to hopper 82. This will then increase the actual feed rate of the apparatus.

Referring to FIG. 5, when the weight of product on supply hopper 82 falls below the weight level required by the control unit 84, a relay in the control unit closes, causing a current to be transmitted to a coil 100. This in turn moves ferrous core 98 and solenoid valve 90 to the right to allow high pressure air to pass from the high pressure port 99, around the reduced neck portion 101 of the solenoid valve 90, and through a passage 102 to the right side of the cylinder 93 moving the piston 94 to the left and thereby moving the conveyor 81 through its feed stroke. An adjusting needle 97 controls the flow of high pressure air to the right side of cylinder 93 and thereby controls the speed of the feed stroke.

When a sufficient amount of product has been fed to the supply hopper the current through coil 100 is cut off and core 98 is moved to the left by means of spring 105 allowing the high pressure air to pass from the cylinder 93 through passage 102 and through drain port 106 to atmosphere. This allows spring 103 to return piston 94 and rack 91 to the right in preparation for another feed stroke. An adjusting needle 96 in port 106 controls the flow of high pressure fluid through passage 106 and thereby controls the speed of the return stroke. An overrunning clutch (not shown) on the shaft carrying pinion 92 permits the conveyor to move only on the feed stroke; it does not move the conveyor backwards on the return stroke. The needle 97 which controls the speed of travel of the conveyor belt should be set as low as possible and yet allow the conveyor to deliver enough product to cause the hopper cell to cut off the conveyor before the end of its full possible stroke. If the belt speed of the conveyor is too fast, the belt will either slide under the product or deliver a full stroke before the hopper cell has time to react. The needle 96 which controls the speed of the return stroke of the rack and piston should be adjusted for a gentle return without shock to the parts when stopping.

The purpose of the supply hopper 82 besides providing a means to control the actual feed rate is to smooth out the product into a continuous bed. Movement of product along the supply hopper is caused by vibrator 58, upon a signal 58 from rheostat 64, by shaking the material .down an incline. Thus a smooth stream of product is formed along the supply hopper. The supply hopper starts and stops in synchronism with the feeder pans.

The feeder pan 57' is driven by two vibrator units 60' and 61 because of the length of the pan. A single vibrator unit could be used with a shorter pan or the product could pass from one pan to the next. With either a one or two feeder pan unit the purpose is to further string out or separate and smooth the flow of product. Since the feeder pans vibrate at the same time as the supply hopper, they can only deliver the amount of product delivered to it by the supply hopper.

The rheostat 64 regulates the amplitude of the feeder pans and supply hopper vibrators 60' and 61 and 58 in a manner similar to that by which the rheostat 64 controls the feeder pan 57 in FIG. 3. However, in the apparatus of FIG. 4 there is one important distinction; the rheostat 64 does not receive a differential output signal to vary the amplitude of the vibrations because in FIG. 4 the differential output is transmitted to control unit 84 instead of to the rheostat. In the apparatus of FIG. 4 the weight at which the vibrators switch from on to off is set into the control relay 62' by weight control knob 66', in a manner identical to that by which knob 66 controls the cut off point in the apparatus of FIG. 3. A signal 76 which continuously transmits from the scale 67 to control relay 62 the weight of product in the dump bucket 72', is matched against the setting of knob 66', for causing signal 76 to the rheostat 64 of the vibrators to be cut off.

In FIG. 4, as in the embodiment shown in FIG. 3 a signal is transmitted from the control relay 62 to the differential indicating the actual time that the feeding pans are feeding the product to the dump bucket 72.

The available feeding time permitted by the packaging machine cycle is fed to the differential in a manner identical to that discussed above with reference to FIGS. 2 and 3. However as mentioned above, in the apparatus of FIG. 4 the output signal from the differential is transmitted to the hopper cell control unit 84. If the signal from the differential indicates that it took too long to reach the necessary weight then the feed rate must be increased. This is accomplished by transmitting the differential output signal to the hopper control unit 84 to change the weight level of the hopper cell 83 below which the hopper cell will cause the product conveyor to start feeding product to the supply hopper. If the differential output signal indicates that the feeder takes too long to feed the necessary weight (that the feeding rate is too low) then the weight setting of unit 84 at which hopper cell 83 causes the product conveyor 81 to start delivering more product, will be increased so that a greater supply of product will be fed to the supply hopper 82.

A feed control indicator 87, like the feed control indicator 74 in FIG. 3, receives a mechanical signal from the differential mechanism to indicate the setting required to maintain the desired feed rate. When the knob 87' on the feed control indicator 87 is at the fully counterclockwise position the hopper cell is calling for minimum weight. There are about two pounds difference in weight on the hopper cell between the two extreme positions of the indicator pointer knob. This. results in about a four pound change in weight of product in the hopper, because the hopper cell weighs the product at one end of the hopper. A two pound range is needed to take care of any variations that occur during the day due to crumb build-up, voltage variations, etc.

The minimum and maximum settings of the hopper cell can be set by adjusting springs on the outside of the hopper cell but the two pound difference will remain. Thus for example one machine might range from 0-2 pounds and another, handling a larger charge, from 13 pounds.

Thus it can be seen that the feed control of the present invention continuously and automatically adjusts the actual feed rate of a feeding apparatus causing it to approach the available feeding rate permitted by the packaging machine cycle. In this manner optimum operating conditions are obtained by maintaining the thinnest possible bed of product and using as much time as the packaging machine cycle permits without allowing the packaging machine to miss bags to often. Accordingly the best possible weighing accuracy and economy of operation are obtained.

Obviously many modifications and variations of the present invention are possible in light of the above teachings.

What is claimed as new and desired to be secured by Letters Patent is:

1. A method for controlling the actual feeding rate of product from a feeding apparatus to a cyclically operable packaging machine having an available feeding time comprising the steps of generating a first signal indicating the available feeding time of the packaging machine, generating a second signal indicating the actual feed time of the feeding apparatus, comparing the first and second signals to obtain a third signal proportional to the difference between the actual feed time and the available feeding time, changing the said actual feed rate in response to the said third signal by an amount proportional to the third signal so that the actual feed time will approach the said available feeding time.

2. A method for controlling the feed rate of a preselected amount of product to a cyclically operable packaging machine having a finite filling period of available feed time during each cycle comprising the steps of generating a first signal of available feed time of the packaging machine, generating a second signal of actual feed time required to feed the preselected amount of product to the packaging machine, comparing the first and second signals to obtain a third signal proportioned to difference between actual feed time and available feed time, changing the actual feed rate in response to the third signal by an amount proportional to the third signal so that the actual feed time will approach the available feed time.

3. An apparatus for controlling the feed rate of a product from a feeding apparatus to a cyclically operable packaging machine having an available feeding time comprising: a means for generating a first signal indicating the available feeding time of the packaging machine, a means for generating a second signal indicating the actual feed time of the feeding apparatus, means for comparing the first signal and the second signal to generate a third signal proportioned to the difference between the said available feeding time and the said actual feeding time, and a means responsive to the said third signal for changing the actual feed rate by an amount proportional to the third signal so that the actual feed time of the feeding apparatus will approach the available feeding time of the packaging machine.

4. An apparatus for controlling the feed rate of a preselected amount of product to a cyclically operable packagaing machine having a finite period of available feed time during each cycle comprising a means for generating a first signal indicating the available feed time of the packaging machine, a means for generating a second signal indicating the actual feed time required to feed the preselected amount of product to the packaging machine, means for comparing the first signal and the second signal to generate a third signal proportional to the difference between the first and second signals, and a means responsive to the said third signal for changing the actual feed rate by an amount proportional to the third signal so that the actual feed time will approach the available feed time.

A method for controlling the feeding rate of a product from a feeding apparatus having a vibrating feeding mechanism to a cyclically operable packaging machine having an available feeding time comprising the steps of, generating a first signal indicating the available feeding time of the packaging machine, generating a second signal indicating the actual feed time of the feeding apparatus, transmitting the first and second signals into a differential mechanism, subtracting the first and second signals in the differential mechanism to obtain a third signal as the output of the differential mechanism representing the difference between the actual feed time and the available feeding time, transmitting the said third signal to a rheostat which controls the amplitude of the vibrations of the feeding apparatus and thereby changing the actual feed rate so that the said actual feed time will approach the said available feeding time.

6. A method for controlling the feeding rate of a product from a feeding apparatus having an intermediate supply hopper between a bulk product storage member and a vibrating feeder pan, to a cyclically operable packaging machine having a predetermined available filling time, comprising the steps of, generating a first signal indicating the available feeding time of the packaging machine, generating a second signal indicating the actual feed time of the feeding apparatus, transmitting the first and second signals to a differential mechanism, subtracting the first and second signals in the differential mechanism to obtain a third signal as the output of the differential mechanism and representing the difference between the said first and second signals, transmitting the third signal to the said supply hopper in the feeding apparatus to change the weight of product received by the supply hopper from the bulk product storage member thereby changing the actual feeding rate so that the actual feeding time will approach the said available feeding time of the packaging machine.

7. An apparatus for controlling the feed rate of a product from a feeding apparatus to a cyclically operable packaging machine having an available feeding time comprising a means for generating a first signal indicating the available feeding time of the packaging machine, a means for generating a second signal indicating the actual feeding time of the feeding apparatus, a differential means for receiving the first and second signals and subtracting the first signal from the second signal to generate a third signal proportional to the difference between the said available feeding time and the said actual feeding time, said feeding apparatus including a feeder pan and a vibrating mechanism mounted to vibrate the said feeder pan, said vibrating mechanism being of variable amplitude, and a means for transmitting the said third signal to the said vibrating mechanism to change the amplitude of its vibrations by an amount proportional to the third signal and thereby change the feeding rate of the feeding apparatus so that the actual feed time of the feeding apparatus will approach the available feeding time of the packaging machine.

8. An apparatus for controlling the feed rate of a product from a feeding apparatus comprising an intermediate supply hopper between a bulk product storage member and a feeder pan, to a cyclically operable packaging machine having an available feeding time comprising; a means for generating a first signal indicating the available feeding time of the packaging machine, a means for generating a second signal indicating the actual feed time of the feeding apparatus, a differential means for receiving the said first and second signals and subtracting the first signal from the second signal to generate a third signal proportional to the difference between the said available feeding time and the said actual feeding time, a product conveyor mounted to transport product from product storage to the feeding apparatus, a feeder pan adapted to transport product from the feeding apparatus to the packaging machine, and a supply hopper located between the said product conveyor and said feeder pan, a hopper cell controlling the weight of product received by the supply hopper from the said product conveyor, and a means responsive to the said third signal for changing the weight of product which the supply hopper receives from the product conveyor by an amount proportional to the third signal, thereby changing the actual feed rate of the feeding apparatus so that the said actual feeding time will approach the available feeding time of the packaging machine.

9. An apparatus for controlling the actual feed rate of a product feeding apparatus to a cyclically operable packaging machine which permits the feeding device to feed only during a portion of the packaging machine cycle, comprising: a first continuously operating synchronous motor, an output shaft adjacent the said first synchronous motor, a clutch means for selectively engaging the first synchronous motor with the first output shaft, means operable when the feeding apparatus is feeding product for causing engagement of the said first clutch means and thereby causing rotation of the said first output shaft while the said feeding apparatus is feeding product, a first gear rigidly mounted on the said first output shaft; a second synchronous motor, a second output shaft, 21 second clutch means for selectively engaging the said second synchronous motor with the said second output shaft, means operable only during the portion of the packaging machine cycle during which the feeding apparatus may feed for causing engagement of the said second clutch means and thereby causing rotation of said second output shaft only while the packaging machine allows the feeding apparatus to feed product, and a second gear rigidly mounted on the said second output shaft, the rotation of the said second gear being opposite to the rotation of the first synchronous motor, the said first and second gears mounted so that their rotation represents a first and second input to a mechanical differential mechanism, a differential output shaft mounted in the differential so that the angular rotation of the differential output shaft is proportional to the difference in the rotation of the said first and second gears.

10. A product handling apparatus for feeding bulk product in predetermined weighted amounts to a cyclically operable packaging machine comprising: a feeding apparatus having a product conveyor mounted to deliver product to the said vibrating feeder pan, a vibrating mechanism of variable amplitude causing vibration of the said vibrating feeder pan, a dump bucket mounted to receive product from the said feeder pan, and a scale mounted to measure the weight of product received in the dump bucket, a differential mechanism, means operable when the vibrating mechanism is operating for transmitting a first signal to the differential mechanism indicating the actual feed time of the feeding apparatus, a cyclically operable packaging machine adapted to receive product from the said dump bucket, said packaging machine cycle permitting a finite period of available feed time during which the feeding apparatus may feed product to the dump bucket, means operable only during the available feed time of the packaging machine for transmitting a second signal to the said dififerential mechanism indicating the available feed time, means for transmitting an output signal from the differential mechanism representing the difference between the said first two signals, and means responsive to the differential output signal for changing the amplitude of vibrations of the vibrating mechanism and thereby changing the actual feeding rate of the feeding apparatus so that the actual feeding time will approach the available feeding time of the packaging machine.

11. A product handling apparatus as set forth in claim wherein the means responsive to the differential output signal is a rheostat which controls the amplitude of the vibrations of the vibrating mechanism.

12. A product handling apparatus as set forth in claim 11 including a feed control indicator, said feed control indicator being responsive to the differential output signal to indicate the setting of the rheostat and thereby indicate the actual feeding rate of the feeding apparatus.

13. A product handling apparatus as set forth in claim 10 including a weight control knob for determining the weight of product in the dump bucket at which the vibrating mechanisms stops the vibrations of the vibrating mechanism.

14. A product handling apparatus for feeding bulk product in predetermined weighted amounts to a cyclically operable packaging machine comprising a feeding apparatus having a product conveyor, a feeder pan, a supply hopper mounted between the said product conveyor and said feeder pan, said supply hopper mounted to receive product from the product conveyor and deliver the product to the feeder pan, said supply hopper having means for controlling the weight of product it receives from the product conveyor, a hopper cell mounted to measure the weight of product on the supply hopper, means operative when the weight indicated by the hopper cell goes below a predetermined level for causing the product conveyor to transport more product to the supply hopper, a vibrating mechanism for vibrating the said supply hopper and the said feeder pan, a differential mechanism, means operable only when the said vibrating mechanism is vibrating for transmitting a first signal to the said differential mechanism indicating the actual feed time of the feeding apparatus, a means for transmitting a second signal to the differential apparatus representing the available feed time of the packaging machine, means for transmitting from said differential mechanism an output signal which represents the difference between the said first two signals, means responsive to the said differential output signal for changing the said predetermined weight level below which the hopper cell causes the product conveyor to transport more product to the supply hopper thereby changing the actual feeding rate so that the actual feeding time will approach the available feeding time of the packaging machine.

15. A product handling apparatus as claimed in claim 14 including a feed control indicator, said feed control indicator being responsive to the differential output signal to indicate the setting of the said predetermined point of the hopper cell and thereby indicate the feeding rate of the feeding apparatus.

16. A product handling apparatus as set forth in claim 14 including a weight control knob for determining the weight of product delivered by the feeding apparatus.

17. A method for controlling the actual feeding rate of product from a feeding apparatus to a packaging machine comprising the steps of generating a first signal indicating a predetermined feeding time, generating a second signal indicating the actual feed time of the feeding apparatus, comparing the first and second signals to obtain a third signal proportional to the difierence between the actual feed time and the predetermined feeding time, chan ing the said actual feed rate in response to the said third signal by an amount proportional to the third signal so that the actual feed time will approach the said predetermined feeding time.

18. An apparatus for controlling the feed rate of a product from a feeding apparatus to a packaging machine comprising: a means for generating a first signal indicating a predetermined feeding time, a means for generating a second signal indicating the actual feed time of the feeding apparatus, means for comparing the first signal and the second signal and generating a third signal proportional to the difference between the said predetermined feeding time and the said actual feeding time, and a means responsive to the said third signal for changing the actual feed rate by an amount proportional to the third signal so that the actual feed time of the feeding apparatus will approach the predetermined feeding time of the packaging machine.

References Cited UNITED STATES PATENTS 2,609,965 9/1952 Kast 222-55 2,882,937 4/1959 Kay 22255 X 2,983,325 5/1961 Moody 22256 X 3,119,525 1/1964 Flynn 22255 3,135,426 6/1964 Muller et a1. 22255 ROBERT B. REEVES, Primary Examiner,

HADD S. LANE, Examiner,