US3545611A - Rebound type checkweigher - Google Patents

Description

I Umted States Patent 1111 [72] Inventor Robert G. Husome [56] References Cited [2500 Woodside Court, Saratoga, UNITED STATES PATENTS [2]] App] No $31 3?" 9507 940,074 11/1909 Schmitt 209/119 Filed Jan- 15, 1969 2,694,310 11/1954 Pounds 73/67 [45] Patented Dec. 8, 1970 Primary Examiner-Richard A. Schacher Attorneys-F. W. Anderson and C. E. Tripp [54] fi gPP JQ ABSTRACT: The degree of filling of cans is checked by aims raw dropping the cans on a preloaded spring wire which deflects [52] U.S. Cl 209/74, the wire from a contact pin. The cans rebound and the wire 73/67, 177/1, 177/210, 209/119, 209/121 reengages the pin. The deflection time of the wire is measured [51] Int. Cl. B07c 5/20 and underweight or overweight cans have their rebound [50] Field of Search 177/210, 1; trajectory altered by flippers actuated in accordance with the measurement of the aforesaid deflection time of the wire.

= 2 54 REJECT K 50 K 1 so go 1 Q :1; 10 0 62. 32 l 12. K so Q =6 AT WEIGHT \CLUTCH AMPLIFIER INVERTER REJECT SCE'Z-l-B OVER WEIGHT PULSE PATENTED use 8 I970 SHEET 3 OF 6 &

uH-n-hil E W Rs mm mm mm B O R eavrga ATTORNEYS PATENTEDuEc 81976 3545611 SHET a- UF 6 a. v r m INVENTOR. ROBERT G. HUSOME BY 0% W01 Emma E o mo 5oz: mm- H m ATTORNEYS SHEET 5 BF 6 I NVE NTOR. ROBERT G. HUSOME ATTORNEYS PATENTEU DEC 8 I976 PATENTED DEC 8 I970 SHEET 8 OF 6 ATTORNEYS REBOUND TYPE CHECKWEIGHER SUMMARY OF THE INVENTION service is quite demanding and prior weight-sensing devices of the I-Iookes Law or spring platform type have not met with universal acceptance in the field, particularly in canneries. For example, if all. the containers in a production line are to be checked, the checking process must be performed at a high speed. This alone is a problem, but the problem is a serious one when the conditions of high sensitivity are to be met. The distinction between a properly filled container and an underweight or overweightcontainer in terms of actual weight variations is quite a small percentage of the total weight of the container and its contents,thereby imposing a demand of high sensitivity on a rapidly operating checkweigher.

Another condition met in practice is that the checkweigher must be capable of operating under adverse physical conditions such as those encountered in a cannery, namely, heat, moisture, foreign matter and gum deposits and the like. These render equipment that appear to be suitable in the laboratory, but unsuitable for production checking in a cannery or similar environment. I

Another requirement is that the production line checkweighers must be relatively trouble free, require little maintenance and that the accept and reject level settings can be introduced by unskilled personnel.

In accordance with the present invention, all of these requirements are met without any of the disadvantages of prior weight-sensing checkweighers referred to above, by an accurate weight-sensing device of the utmost simplicity. The general principle of the device takes advantage of the physical characteristics of an oscillating system comprising a spring set into harmonic motion while loaded with the mass of the article to be weighed. By measuring the time interval for one-half cycle' of a period of vibration of the system, a weight determination is provided, and by an essentially simple apparatus. Furthermore, the weight determination is independent of variations in the approach speed at which the articles are fed to the spring. a

More specifically, in the preferred embodiment of the present invention, the spring is' in the form of a generally horizontal, preloaded wire which in its initial position engages an electrical contact pin. The articles to be weighed (such as cans) are rolled up a ramp to symmetrically distribute their product and successively dropped on the wire adjacent to the contact pin. When the cans engage the wire, a vibrating system is produced that operates under the laws of harmonic or periodic motion. See Classical and Modern Physics" by White, page 174, D. Van Nostrand Co., Inc., New York, I940.

In the present invention, advantage is taken of the isochronous nature of the vibratory motion that takes place between the time that the can first strikes the preloaded wire and the instant that the wire and can return to the initial position of the wire, that is, against the electrical contact pin. Under the present invention, it was recognized that the deflection time of the wire, if it were to be measured, would be a direct function of the mass of the article that was undergoing a half cycle of periodic vibration in the vibratory system thus established, and hence could be used to indicate the weight of the article. It was also recognized that this system would be isochronous, that is, not dependent upon the drop height of the articles, but only'on their mass.

Another feature of the present invention is in utilization of the rebound trajectory of the articles (e.g. cans) being weighed as forming part of a sorting system. After the spring wire returns to its initial preloaded position and in contact with the contact pin previously mentioned, the kinetic energy imparted to the wire spring system due to the falling of the cans on the wire, is reimparted to the cans so that the cans assume a trajectory complementary to that which they followed when falling on the wire. Thus, it is possible to drop the cans while they have forward momentum, and to catch the cans downstream of the wire contact zone after they have been weighed by the wire. In order to sort out cans which are not at weight, in the preferred form, the trajectory of such cans is boosted by a flipper that is actuated in response to the weight signals obtained from the measurements of the deflection times of the wire while they are supporting the cans.

In the preferred embodiment of the present invention, at weight cans are caught on a chute or conveyor that intercepts their normal rebound trajectory. The boosted trajectory for rebounding underweight or overweight cans is intercepted by a different chute. Also, in accordance with the preferred embodiment of the invention, the flipper is rotated once upon each measurement of an underweight or overweight can by a one revolution clutch, and hence is immediately returned to its ready position for operation in accordance with subsequent underweight or overweight signals.

Thus a high speed, sensitive sorting device is provided in the form of mechanism that is not sensitive to its environment. The system wherein the deflection time of the can-spring wire system is converted into weight-sorting signals includes an electronic circuit. This circuit provides adjustable RC timing components for determining the respective differences between the deflection times of underweight and overweight cans relative to that of a can which is at weight. Thus the sorting system of the present invention can be adjusted for weight variation limits by operating personnel at a production line.

DESCRIPTION OF THE DRAWINGS Brief Description of the Drawings FIG. 1 is a diagram showing a rebound-type checkweigher of the present invention incorporated in a system for checking the weights of containers such as cans.

FIG. 2 is an enlarged detail showing the action at the contact pin.

FIG. 3 is a partial plan of the apparatus.

FIG. 4 is a side elevation taken on line 4-4 of FIG. 3.

FIG. 5 is an enlarged schematic diagram illustrating the operation of the device when the article is at weight.

FIG. 6 is a similar diagram showing the rejection of an underweight or overweight article.

FIG. 7 is a schematic diagram of a deflection time measuring circuit.

FIGS. 8 and 9 show modified springs.

DETAILED DESCRIPTION OF THE INVENTION General Organization FIGS. l4 illustrate the invention applied to a system for sorting containers such as filled tin cans by weight. The cans K are fed to the checkweigher while standing on end by means of a lead-in rail conveyor 10 which has a twisted rail section 12 that turns the cans into a rolling position on their sides. The cans roll over a free wheeling star wheel 14 which separates the cans somewhat (to provide measurement intervals) as they enter an upwardly inclined ramp in form of laterally spaced tracks 16. Side plates 17 confine the cans axially. The cans It are rolled up the ramp 16 while maintained in their spaced position by a friction belt 18 having an idler 20 above the star wheel 14 and a drive pulley 22 driven by a V-belt pulley 23 and motor 24 (FIG. 3).

The inclined ramp terminates in a downwardly inclined ramp or dropoff in the form of laterally spaced continuations 28 of the ramp sections 16. The structure thus described provides means for delivering the cans to be weighed to the preloaded spring forming part of the present invention, previously referred to. The rolling action along the ramp distributes the contents symmetrically in the cans.

In the preferred embodiment of the invention the preloaded spring is in the form of a steel wire 30 anchored to a post 32 at one end which post may also represent the ground of the electrical deflection time-measuring circuit. The wire is in the vertical plane of the center ofgravity of the falling cans. The wire passes from the post, between the track sections 28 and 16, and is pulled around a pulley 34 on the frame (FIG. 4) by a preload spring 36. One end of the spring is looped to the wire 30 and the other end is adjustably mounted to the base of the machine by a threaded eye bolt at 38 (FIG. 4).

An important featureof the embodiment of the invention being described is provision of an electrical contact pin 40, which is engaged by the wire 30 when the wire is in its initial or can receiving position, that is when the wire is undeflected by a measuring operation. Thus the wire 30 and the contact pin 40 act as a deflection time-measuring switch. This switch is connected to a weight signal generating the circuit to be described in detail presently, and which is shown functionally in the block diagram of FIG. 1.

The pin 40 is mounted on the base of the machine by an insulating block 42 and a lead 44 extends from the pin for connection to the weight signal circuit.

Down the siream from the dropoff plates 28 is a cancatching or re ceiving ramp in the form of laterally spaced ramp plates 50 and in the embodiment of the invention being described these plates receive cans on the rebound that are at weight, Above the ramp plates 50 are reject ramp plates 54 which receive cans with the assistance of flippers to be described.

As seen in FIG. 1 the at weight" ramp plates 50 lead to a can twisting conveyor 56 complimentary to the conveyor 10, and which twists the cans back into their upright position in a manner well known in the can conveying art. The reject ramp 54 delivers cans to a chute or other receptacle for removal from the main stream of the production line.

The pair of spaced guide plates 58 prevent inadvertent or occasional bouncing of cans out of the machine, and upon rebound, rejected cans may ride along the curved under surfaces 59 of the side plates 58.

One of the features of the present invention is that in the preferred embodiment, cans which are at weight are delivered to the take away conveyor ramp 50 by the normal rebounding action of the forwardly moving cans on the wire 30. In other words; the can receiving end of the at weight conveyor t) intercepts a terminal portion of the trajectory of the rebounding cans.

Another feature is that of giving rejects a trajectory that terminates at the upper conveyor 54, without denting the cans. Flipper arms 60 are provided just inside of the ramp sections 50 for this purpose. The flipper arms are pinned to a common shaft 62 which is connected to one element of a solenoid operated l-revolution clutch 64. The other element of the clutch is constantly driven by a pulley 66 and a continuously rotating motor 68 (FIG. 3). The clutch solenoid S actuates a pawl mechanism 70, the actuation which causes clutch engagement for exactly one revolution of the clutch shaft, whereupon the clutch is released and the flippers 60 have returned to their initial position. The energization time of the clutch solenoid can be less than that required for one clutch revolution. The details of the l-revolution clutch are not critical to the present invention, devices of this sort being known in the mechanical arts and hence such details are not illustrated herein. The solenoid S for the clutch has leads 72. and 74 that connect to the deflection time-measuring and reject circuit, to be described.

Although the details of the deflection time-measuring circuit are not critical to the present invention, a circuit has been found to operate satisfactorily and which is illustrated in FIG. 7, is diagramed schematically in connection with FIG. ll. Referring to FIG. 1, the wire 30 and the contact pin 40 form a grounding switch, the condition of which is sensed by an amplifier inverter. This current, in response to opening and'clos' ing of the switch sends pulses to an underweight and an at weight circuit and into an overweight circuit. Timing circuits including rheostats RI and R2 are provided, and the adjustment of these rheostats determine the limits "for under and overweight conditions relative to a selected at weight condition of the articles being weighed. The rheostats R1 and R2 are calibrated and made accessible to the operator of the machine.

When the wire opens the circuit, signals are sent to the at weight, underweight and overweight circuits but the at weight" circuit disables the underweight circuit. The overweight circuit is not disabled by the at weight" circuit, but is reset by the wire retouching the pin when the cans are at weight", If the can is not at weight, a signal is sent from either the underweight or the overweight circuit to an OR gate, which sends a reject pulse to a solenoid driver circuit. The latter, through the leads 72, 74 previously mentioned energizes the reject clutch solenoid S, engages the clutch 64 and causes a single revolution of the flippers for placing the under or overweight cans in the upper ramp 54. When the wire recloses the switch, the amplifier-inverter is grounded again and this resets the circuit for the next measurement. This action must all occur within a period of time that is less than that represented by the time required for successive cans K to pass a given point along their trajectory during the mea suring operation.

Rebound Action FIG. 5 is an enlarged schematic diagram illustrating the trajectory of a single can (all positions in solid lines) which is at weight" and hence requires no action by the flippers 60. The single can is shown in a number of positions in FIG. 5 each of which is indicated by a small letter in parenthesis. The can at position a is nearing the drop off portion of the ramp plates 16. At 11 the can is at its zenith, ready to drop onto the wire 30. The can has a certain horizontal forward velocity and this velocity coupled with the force of gravity will cause it to move down the descending ramp 28 without any substantial rolling action against the ramp, due to friction between the ramp and the can; Position c shows the can descending the ramp.

The can strikes the wire 30 with the latter in its initial preloaded condition and touching the contact pin 40, this position of the can being indicated at d. The can continues downwardly along its trajectory thereby deflecting the wire 30 from the pin 40 until the can reaches its lowermost position indicated at e. At this time the wire will have deflected from the pin 40 a distance indicated at x but as will be explained the magnitude of the distance at x is not significant. The significant factor is the total deflection time required for the wire to deflect the distance x and back against the pin 40,

While the wire is being deflected by the can the vertical mo mentum of the can is being stored as energy in the spring system of the wire, and when the wire reaches its lowermost position this energy is restored to the can by the wire spring system, raising the can back until the wire again touches the pin 49 at its initial preloaded position. The can now will be at position f in the FIG.

Since the can was dropped at a height H onto the wire, the energy acquired during falling will be substantially restored to the can and it will rebound or continue upward along the complementary rebound trajectory illustrated, which includes vertical as well as forward components. An intermediate portion of the rebound trajectory is indicated at g, and at position It the can will have reached its maximum height which is sufficient to clear the height I of the ramp 50. The can then continues its forward motion under the momentum imparted by the conveyor 18 and now fall slightly as at i until it is received by the ramp 50 at position j. The can rolls down the ramp as at k, for delivery to the takeaway conveyor 56 (FIG. 1).

The timing circuit measures the time during which the wire is deflected. If the time is too short the can is underweight and if it is too long it is overweight. When the can is at weight the underweight reject circuit is disabled and hence, as shown in FIG. 5, the flipper 60 remains stationary during rebound of a can in its at weight condition.

Under or Overweight Cans FIG. 6 illustrates the rebound action of the weighing device when the cans are either over .or underweight, although the trajectory is for an overweight can. Under these conditions the can has a greater mass than an at weight can and hence for a given drop H the wire 30 is deflected by a distance y from the pin 40, which is greater than the distance .1: representing the deflection by an at weight can. Of course this assumes that all delivery conditions are the same for both cans but actually precise delivery is not critical to precise measurement under the invention. The essential feature of the invention is that the time required for the wire to b e deflected through the distance y and back, when the can is overweight, is longer than that required for it to be so deflected when the can is at weight or underweight.

The positions of the cans a through d shown in FIG. 6 are substantially the same as in FIG. 5. However, at e the can is lower than before because it is overweight. Upon rebound, and soon after the wire 30 touches the pin 40, the flippers 60 begin to rotate. The flippers move up under the can and give it an upward boost as illustrated in positions j g' and h in FIG. 6. Of course it is understood that the exact trajectory of the cans and that their contact zone with the flippers 60 is not readily determinable and is not in fact critical. The essential feature of the invention is that the flippers 60 do impart a higher or boosted trajectory to the cans so that they will reach a position j which is above the upper reject ramp 54. The overweight can (in this case) then falls on the ramp at k and rolls down to takeaway system for underweight or overweight cans. Actually the under surfaces 59 of the side plates 58 may guide the rejected cans over the reject chute 54. This makes it possible to provide an adequately strong boost with the flippers 60 without flipping the cans so high that they fall an undesirable distance onto the reject ramp 54.

The rejection of underweight cans is not illustrated but corresponds to the diagram of FIG; 6 except that the trajectory is somewhat different in that the wire is deflected by the can a distance (not illustrated) which is less than the distance x representing the deflection caused by an at weight can. Again it is to be pointed out it is not the distance of deflection that is critical, but the time that elapses between the time when the wire initially is deflected away from the contact and the time when it recloses the contact 40.

Thepreloaded wire 30 is so mounted and the pin 40 so positioned relative to the descending ramp 28 that the deflection action on the preloaded wire by the can between the time the wire leaves the pin and reengages the pin represents a discursion over substantially one-half cycle of a simple periodic or harmonic motion of a vibrating spring mass. This period T is given by the expression:

In the above, m" can represent the mass of the can in question in grams, and k in this expression will be a number expressing the stiffness of the spring represented by the wire 30 and the preload spring 36. The number k" can be expressed in terms of the dynes required to deflect the spring assembly one centimeter at the can impact zone. T will then be in seconds.

Examination of the above expression and consideration of the physics involved reveals that the period or deflection time T is determined solely by the mass m of the can and the spring constant k. This is an important advantage of the present invention. The spring-mass system whose characteristics are being measured and converted into can mass is essentially isochronous. This renders the system substantially independent of the velocity of successive cans as they strike the wire 30 during the measuring process.

Pin Position The measuring principle depends upon causing the springarticle system to have a vibratory excursion of one-half cycle which requires that the vertical position of the pin 40 be carefully chosen. Basically, the pin 40 will be positioned vertically so that it just touches the wire 30 when the latter is statically loaded by an at weight article. This will cause a vibration excursion of one-half cycle during dynamic operation and will serve as an adequately preuse base for underweight and overweight measurements. Simple initial tests can be made in each installation to find the proper pin position for -cycle mea surement.

DEFLECTION MEASURING AN D REJECT CIRCUIT FIG. 7 diagrams a deflection measuring and reject circuit which has been found suitable for connection to the wire 30 and the contact-pin 40 and to the reject solenoid S of the one revolution clutch that operates the flippers 60.

As previously mentioned, the reject solenoid S is triggered from an OR gate that delivers a pulse to the solenoid driver circuit for either underweight or overweight cans. The reject pulse'fires a silicon control rectifier SCR-2 in series with the solenoid S and a volt current supply in response to the reject pulse.

The timing portion of the measuring circuit includes two RC timing circuits including the rheostat R1 and a capacitor C1; and the rheostat R2 and C2. The general principle of operation of this circuit is as follows:

During deflection of the wire from the pin, the capacitors C1 and C2 of the two RC circuits begin charging. If the can being measured is at weight", the capacitor ofRl, C1 timing circuit will become charged to a voltage high enough to disable the underweight reject circuit just before the wire 30 retouches the contactpin 40 on rebound. Thus the rheostat R] can be adjusted to select a predetermined deflection time for the wire which represents acceptable can weight.

If the can is underweight, the R1, C1 circuit cannot charge to the at weight" voltage before the wire retouches the pin, and hence the at weight circuit does not disable the underweight reject circuit. An underweight can will provide a deflection time long enough to charge the capacitor C1 to a point sufficient to provide an underweight reject pulse when the wire retouches the pin on rebound of the underweight can.

In fact, the circuit will reject an empty can. For example, the weight of a full can may be about 10 times that of an empty can. Under the formula, the deflection time will only be larger by **l0. This range in deflection times is readily handled by the circuit.

As to overweight cans, the deflection time for a can which is at weight" is not sufficient to charge the R2, C2 timing circuit capacitor sufficiently to provide an overweight reject pulse before the wire recloses the switch on rebound and resets the circuit. An overweight pulse can only be provided when the deflection time is longer than that determined by the R1, C1 circuit for a can which is at weight.

Having described the general principles of operation, the more significant circuit elements will not be explained. Circuit details representing the mere circuit design will not be described, but reference is made to the appended table which gives typical circuit values.

7 CIRCUIT DESCRIPTION Wire-Touching Pin O1 is an amplifier and inverter NPN transistor with its base normally grounded by Contact 40 and the wire 30, so that R11 supplies no forward bias. Q2, 3 and 4 as well as SCR-l are all part of the at weight" and underweight comparison circuit. They are connected to a +30 volt supply, as indicated. As mentioned, R1 is the variable resistor of the R1, C1 timing circuit that adjust the internal time standard.

Normally the wire touches the pin 40, grounding the base of transistor 01 and hence Q1 is rendered nonconductive so that its collector voltage at RU is high. This collector voltage is applied to the bases of trarsistors Q2 and 03 (as well as to Q5 in the overweight circuit) via their respective resistors R9, R and RIOA, rendering transistors Q2, Q3 and Q5 conductive.

R1 provides charging current for the timing capacitor C I, provided that the capacitor is not shunted by conduction of 02. However, when the wire engages the pin 40, Q2 is conductive and hence C1 not permitted to charge, or at best the voltage across C1 remains very low. The same applies to the overweight timing cap: citor C2.

As mentioned, transistor Q3 also conducts when the wire touches the pin. The collector of O3 is connected directly to the anode of a silicon controlled rectifier SCR-l so that with O3 conducting, the anode is grounded, holding SCR-l turned off. Q3 can be considered to act as a reset transistor for the silicon controlled rectifier SCR-l.

O4 is a unijunction transistor with its emitter connected to Cl. As long as Q2 remains conductive (wire-touching pin), voltage cannotbuild up on C 1 andhence on the emitter of Q4, so that the peak-point voltage of O4 is not attained, it is not forward biased, and hence Q4 cannot fire. 1

Wire Clears Pin When a can contacts wire 30', pin 40 is cleared, applying a positive current to the base of Q1 through R11 and hence causing Q1 (which was cut off) to become conductive. The voltage at the collector of Q1 drops almost to ground potential, lowering the base bias to Q2, Q3 and Q5 via R9, R10 and RNA, rendering these transistors nonconductive With Q3 cut off, the anode of SCR-l is no longer grounded, and anode voltage is applied to SCR-l via R13. However, the unijunction 04 has not yet fired, and hence no injector voltage has been applied from base B1 of the unijunction Q4 to SCR- l, and the latter continues to remain nonconductive. Nevertheless, since Q2 was cut off when the wire 30 left the pin 40, CI is now charging toward the +30 volt supply, the charge rate being determined by the setting of R1.

Can Not Underweight Wire Clears Pin If the can being measured is not underweight the following sequence takes place: Cl continues to charge until the voltage across Cl reaches the peak-point or firing voltage of the unijunction transistor Q4. Q4 fires, partially discharging the timing capacitor C 1 through its base Bl resistor R4, thereby generating a positive pulse of voltage across its base Bl resistor R4. This positive pulse is coupled via an RC network R15, C3 to the gate or injector of SCR-l, causing it to fire through its grounded cathode. When SCR-l conducts to ground, its anode voltage drops to near ground potential but SCR-l remains conducting because R13 supplies enough current from the +30 volt source to the anode of SCR-l to hold it in its conductive condition.

The R1, Cl timing circuit is adjusted so that a wire deflection time'long enough to charge Cl sufficiently to trigger the unijunction Q4 (as just described) represents a deflection time which can be translated into a can that is at least at weight". Hence the underweight reject circuit should be disabled before the wire retouches the pin. To accomplish this, the anode of SCR-l is connected via a diode D1 and a current limiting resistor R5 to the timing capacitor C1. With SCR-l conducting, this circuit discharges C1 to near ground potential, this circuit discharges C1 to near ground potential. There can now be no underweight reject pulse.

The timing capacitor CZirI the overweight reject circuit has not had time to charge to a reject voltage.

Wire Returns To Pin Soon after C1 has been discharged by SCR-l, (can at least at weight) the wire retouches the pin as the can under'measurement bounces away from wire. The base of O1 is now regrounded, cutting off Ql and with Q1 cutoff the collector of 01 again becomes positive through R12 and Q2, Q3 and OS are again returned to their conductive state. Q2 now discharges C1 to ground via its emitter current limiting resistor R3, but since there was very little charge left on C1 (due to the drain through D1 and R5 by SCR-l )very little voltage is developed across the emitter resistorR3 of Q2. Although the small pulse across R3 is passed on to'diode D2 of the OR gate, the pulse does not develop enough voltage across R7 of that gate to trigger the reject rectifier SCR-2. No underweight reject can occur.

When the reset transistor Q3 was again made conductive by the wire returning to the pin at the end of the measuring interval, Q3 again grounded the anode of SCR-l (25) and caused SCR-ll to extinguish, resetting the entire circuit and preparing it for the next measurement.

Thus it can be seen that when a can is .at weight, the timing capacitor C1 is discharged before the wire retouches the pin, and that no underweight reject pulse is generated. As mentioned, the overweight deflection-meauring capacitor C2 will not have charged sufficiently to produce an overweight reject pulse before the wire retouches the pin and resets it circuit.

. Underweight Can Wire Touches Pin The current condition is initially as previously described with Q); cutoff, Q2 and Q3 conducting, unijunction O4 is not firing and SCR-l not conducting. O5 in the overweight circuit is also conducting, thereby grounding the overweight timing capacitor C2. Of course the reject solenoid S is not energized at this time.

Underweight Can Reject Pulse Although the can under measurement is underweight, the

initial phases described for at weight".cans take place. The

wire leaves the pin 40 when the can drops onto the wire. Q1 again becomes conductive rendering Q2 and Q3 nonconductive. Timing capacitor C1 starts charging toward +30 volts as before. The overweight transistor O5 is also cut off by Q1 when the wire leaves the pin 40, charging'timing capacitor C2 through R2, but as will be seen, this charge is not permitted to affect the reject circuit. However, the deflection time of the wire (which decreases as the square root of the mass) is now shorter than before, so that the wire reengages the pin 40 sooner than in the caseof an at weight can. Rheostat R1 will have been adjusted so that before C1 charges through R1 to'a voltage sufficient to fire the unijunction Q4, the wire will have reengaged the pin 40. This renders Q1 nonconductive and Q2 and Q3 conductive. Q2, being conductive, will now discharge whatever charge had accumulated on C1, through its emitter resistor R3. The discharge of a substantial charge on C 1 through R3 creates a positive reject pulse across the emitter resistor R3. This positive reject pulse is passed on to the diode D2 of theOR gate, indicating that an underweight condition existed, and the reject relay SCR-2 is fired in a manner to be described.

The time constant of the overweight timing circuit R2, C2 is long enough so that C2 cannot be charged to its trigger voltage during the deflection interval of the wire caused by an underweight can.

Overweight Can Retouches Pin The initial conditions are as before, 01 grounded to cutoff, Q2 and Q5 conducting, and no charge being permitted to accumulate on timing capacitors C 1 and C2.

Overweight Can Reject Pulse The overweight comparison circuit consists of the transistor 05, the unijunction transistor Q6, and their associated components As mentioned, C2 is the overweight timing capacitor and R2 is the adjustable timing resistor which permits adjustment of the internal time standard for overweight cans. At the beginning of the deflection time interval,the wire leaves the pin 40, 01 becomes conductive and Q5 nonconductive. With Q5 cut off, C2 starts charging toward the +30 volt supply via R2 at a rate determined by the setting of R2.

As mentioned previously, if the can under measurement is not overweight Q5 will be returned to its conductive state before the voltage developed across C2 becomes high enough to tire 06, the unijunction transistor.

However, if the can under measurement is overweight, Q5 remains nonconductive for a longer period of time (longer wire deflection time), allowing the voltage across C2 to reach a value sufficient to fire the unijunction 06. When 06 fires, conduction to ground takes place through R15, Q6 and the base Bl resistor R6. Thus a positive pulse is created across resistor R6, which is the overweight reject pulse that is fed to the diode D3 of the OR gate.

During the interval just described the at weight" cycle will have been carried out also, reducing the charge on the capacitor CI to disable the underweight reject circuit, but this has no effect on the overweight circuit.

Wire Reengages Pin Just after the overweight reject pulse is delivered and hence at the end of the timinginterval, the wire reengages the pin 40, O1 is cut off, 05 again becomes conductive and discharges the overweight timing capacitor C2 to ground through the emitter resistor R16 of 05. This resets the circuit and prepares the overweight circuit for the next measurement. However, an overweight reject pulse will have been delivered.

Solenoid Driver Circuit The solenoid driver circuit includes silicon-controlled rectifiers SCR-Z, SCR-3 and their associated components. The solenoid S in the anode circuit of SCR-2 (F IG. 7) is the single revolution clutch solenoid. When the +l50-volt source is applied to the solenoid driver circuit the anodes of SCR-2 and SCR-3 go positive toward +l50 volts through S and R8, respectively. Lacking a signal on its gate, SCR-2 will not fire. However, when the anode of SCR-3 reaches approximately 75 volts the neon bulb Ne ionizes and applies a positive pulse across R17 to the injector gate of SCR-J, causing it to fire, and conduct to ground. When SCR-3 fires it anode voltage drops to a very low lever and the bulb Ne is extinguished. The firing of SCR-3 also momentarily applies a negative going pulse to the anode of SCR-2, but with no consequence. Although Ne is extinguished. SCR-3 remains fired because the current supplied to its anode via R8 is sufficient to hold it in the conductive state. The capacitor C4 is charged through the clutch solenoid S, but this charging circuit is not enough to energize the solenoid. Therefore in steady state conditions, SCR-2 is turned off and SCR-3 is turned on, C4 is charged and the clutch solenoid S is not energized sufficiently to activate the clutch.

When a positive reject pulse is received from the OR gate and applied to the injector of SCR-2, SCR-2 turns on and a power circuit to ground is completed through the solenoid 5. Also, when SCR-Z turns, C4 is discharged through SCR-Z. and a negative voltage pulse is applied to the anode of SCR-3, which causes SCR-J to turn off.

The silicon-controlled rectifier SCR-2 continues to conduct current since the current flowing from the source through the solenoid S is sufficient to hold SCR-2 in it conductive state. The left side of C4, which is connected to the anode of SCR-2, remains near ground potential when SCR-2 is conducting to ground. However, C4 now starts charging toward +1 50 volts via R8. After a period of time determined by C4 and R8, the right tenninal of C4 will reach approximately 75 volts at which time the neon bulb' Ne will again ionize and conduct through R17 to ground..This applied a positive pulse to the injector of SCR-3. SCR-3 will turn on, dropping its own anode voltage to near ground potential. C4 now discharges to ground through SCR-3, which applies a negative pulse to the anode of SCR-2. This causes SCR-2 to turn off, and the anode voltage of SCR-2 will quickly rise to +150 volts because curby the values of C4 and R8. The driver circuit time constants are such that for underweight cans the pulse is applied to the solenoid S immediately after the wire 30 retouches the pin 40 and the can'is rebounding. For overweight cans, the reject pulse will occur just an instant earlier. The solenoid driving circuit pulse has a finite duration to insure timed clutch actuation.

When the clutch solenoid S is energized the clutch 64 is immediately engaged, raising the flippers 60 against the can. The can is boosted into its reject trajectory but the solenoid S is deenergized after something over a half revolutions of the flippers, allowing the clutch mechanism (not described) to disengage and to stop the flippers mechanically after one revolution. it is to be noted that the flipper motion will not change the direction of thecan, it need only boost its acceleration in the direction of can motion. This requires a relatively small booster forceand does not dent the can.

The spring constant k can be selected for a given nominal can mass m" to provide a half cycle time T that is quite short, a fraction of a second. The timing circuit can be easily designed and set to carry out its functions in this short time period.

The Design Tables given below give data on a typical apparatus sufiicient for those skilled in the art to practice the invention.

DESIGN TABLE CIRCUIT TABLE Q1, 2, 3 and 5NPN transistor, type 2N3904. Q4 and 6Unijnnction transistor, type 2N4870. SCR-l, 2 and 3Silicon controlled rectifier, type R1 and 2Variable, set at approx. 27K ohms. R3 and 16-150 ohms.

R4 and 6100 ohms.

R5 10 ohms.

R827K ohms.

lt92.4K ohms.

C l RC U lT TABLE -Continued R and 10A24K ohms. R11270K ohms. Rl212K ohms. R13 -5.6K ohms.

R14 and 151.3K ohms. R17-1K ohms.

MODIFIED EMBODIMENTS in the embodiment of the invention previously described, objects such as tin cans were dropped on a stretched wire for weighing. This weighing assembly is so precise that the drop height of the articles can be relatively small and hence the even fragile articles such as filled tin cans can be dropped on the wire spring and rebounded therefrom without denting the cans. However, if it were desired to provide a larger contact area during the rebound action, the modified spring assembly of FIG. 8 could be employed. Here the spring 30a, instead of being a wire, is a thin steel band anchored to the post 32a and hence to the frame of the machine. The contact pin assembly 400, 42a and the lead 44a are as before. The other end of the band 30a connects to a coil spring 36a as before which is adjustably tensioned by an eye bolt and nut assembly 38a secured to the frame. The force of the coil spring 36a is transferred to the band means of a pin 80 extending through a loop in the band and mounted on arms 82 pivoted at 84 to the frame. A triangular wire link 86 connects the arms 82 to the spring 36a. The mode of operation of this modification will be obvious and is substantially like that previously described.

FIG. 9 shows a cantilever spring 30b which is preloaded by the contact pin 40b mounted in an insulating block 4 2b and having a lead 44b for connection to the electronics. The base of the cantilever spring 30b is secured to a post 90 which is rotatable in support brackets 92 mounted on the frame of the apparatus. The preloading force on the spring 30b can be adjusted by turning the post in the desired direction and clamping it in its adjusted position by set screws 94 which clamp the ripest 90 to the post supports 92. A lever 96 is provided for T facilitating preload adjustment of the spring before tightening the set screws 94. The mode of operation of this device is essentially the same as that previously described and hence is not repeated in detail.

It can now be seen that my invention provides a weighing device which is both precise and free from mechanical jamming, clogging or other disabling conditions thus the device lends itself to sorting operations in canneries or the like which have previously presented environmental difficulties. It has also been found that precision weight measurements can be made on objects that are easily dented, such as filled tin cans or the like. As previously pointed out the accuracy of the measurements performed by this device, when employed in a sorting apparatus, is independent of the velocity imparted to the articles in either the forward or the vertical direction before they fall against the wire or other spring system of the apparatus.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention as set forth in the appended claims.

Iclaim:

l. The method of weighing an article comprising the steps of dropping the article on a preloaded spring with the center of gravity of the article lying substantially in the plane of spring deflection, measuring the time required for the spring to deflect and return to its preloaded position while the spring. is supporting the article, and converting the deflection time so measured into an article weight signal.

2. The method of claim 1, wherein forward momentum is imparted to the article before it is dropped, and the article is caught on rebound downstream of its zone of support by the spring.

3. The method, of claim 1, wherein the deflection time rebounding containers of another weight andat another loca tion by intercepting their boosted rebound trajectory.

5. The method of sorting a succession of articles by weight comprising the steps of determining the mass of the objects rebounding them from a preloaded spring, intercepting the normal rebound trajectory of articles of one mass for sorting out those articles, and boosting the normal rebound trajectory of articles of another mass for sorting out those articles. 5

6. The method of claim 5, wherein a horizontal momentum is imparted to the articles during their rebound.

7. The method of claim 5, wherein the mass of the articles is determined by measuring the deflection time of the spring while it supports each article.

8. The method of claim 7, wherein the deflection time of the spring is caused to be substantially one half of the period of the vibrating spring article mass system.

9. Checkweighing apparatus comprising a spring, means for preloading said spring to a predetermined initial position, means on said spring for intercepting falling articles to be weighed, means fordropping an article on the article intercepting means of said spring with the vertical plane substantially through the center of gravity of the article passing through the plane of spring deflection, means for measuring the deflection time during which the spring is deflected from its initial position while supporting the article, and means for converting said deflection time intoa weight signal.

10. The apparatus of claim 9, wherein said deflection timemeasuring means comprises an electrical contact responsive to deflection of spring from initial position, and a time-measuring electric circuit that determines the period of time during which the spring is deflected from its initial position and converts such time period into the weight signal.

11. Apparatus for sorting a succession of articles by weight comprising an elongated preloaded spring, conveyor means for imparting horizontal momentum to a series of spaced articles and dropping them on said spring, means for catching the rebounding articles downstream of their zone of support on said spring, means for measuring the deflection time of the spring while it supports an article, and means for sorting the articles in accordance with their deflection times.

12. The apparatus of claim 11, wherein said sorting means comprises a one-revolution article-boosting flipper.

13. Apparatus for sorting by weight a succession of articles of uniform shape and size, such as filled containers, comprising a generally horizontal spring wire, means supporting said wire by its ends and under a preload so that an intermediate portion of the wire normally assumes a predetermined article intercepting position, means for dropping a succession of the articles on the intermediate portion of said wire for causing the wire to be deflected from its article-intercepting position, means for measuring the time during which the wire is so deflectedwhile supporting each article, means for converting said deflection time into article weight signals, means for catching articles of one weight in their normal rebound trajectory, article deflector means for altering the normal rebound trajectory of articles of another weight, and means for operating said article deflector means by said article weight signals.

14. The apparatus of claim 13, wherein said article deflector means boosts the normal rebound trajectory of articles of another weight.

15. The apparatus of claim 13, wherein said articledropping means is a conveyor that imparts a horizontal momeans comprises a one revolution flipper controlled by said deflector operating means.

18. The apparatus of claim 14, wherein guide means limit the altitude of the boosted trajectory.

253 3? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,545,611 Dated Dggembg: 8 1210 Inventor(s)ROBERT G. HUSOME It is certified that error appears in the above-identified patem and that said Letters Patent are hereby corrected as shown below:

Column 6, line 61: change "**l0" to 41 Column 7, line 75: delete ",this" (second occurrence) anc insert Column 8, line 1: delete "circuit discharges Cl to near ground potential";

line 30: change "meauring" to measuring;

line 32: change "it" to its.

Column 9, line 9: insert a period after "components Column 10, line 17: change "105" to --l50.

Signed and sealed this 28th day of December 1971 (SEAL) Attest:

LBDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Patent:

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