US 3855919 A
A control system for a compacting machine is provided which includes a compaction chamber into which material to be compacted is placed, a pressure plate spanning the area of the chamber for compressing the material, and a reversible drive source for moving the pressure plate in forward and reverse directions within the chamber. The control system selectively enables driving of the pressure plate to effect performance of baling, packing and return cycles of the machine and provides output indications of the operating condition of the machine, the direction of movement of the pressure plate, and the full condition of the compaction chamber. A time delay circuit automatically shuts down the machine when any of the operational cycles continues beyond a predetermined time limit.
Claims available in
Description (OCR text may contain errors)
Potter  CONTROL SYSTEM FOR A coMPAcnNG MACHINE Richard W. Potter, Downers Grove, Ill.
Assignee: McGraw Edison Company; Elgin;
Filed: Aug. 21, 1972 Appl. N O.Z 282,413
 I lnventori  US. Cl...'. 100/52, 100/3, 100/53,
w ns]; Dec. 24, 1974 FOREIGN PATENTS OR APPLICATIONS 321,570 1111929 GreatBritain ..l00/256 Primary Examiner-Billy J. Wilhite Attorney, Agent, or Firm-John L. Parker [57 ABSTRACT A control system for. a com'pacting machine is provided which includes a compaction chamber into which material to be compactedis placed, a pressure I fplate spanning the area of thechamber for compress- 100/99, 100/215, 100/218, IOU/269 R, 200/6162 ing'the material, and a reversible drive source 'for  Int. Cl B30 b-f15/1'6 moving the pressurejfplate in forward and reverse di-  Field of Search..'..... ZOO/61.62; 335/205; e s it vthe ch m The nt o y te e ec- 100/52, 50, 53, 99,256, 3, 8,- 215, 218, 269 tively enables driving of the pressure plate to effect a I l R Y performa nce of baling, packing and return cycles of the machine and provides output indications of the  References Cited operating condition of the machine; the direction of UNITED STATES PATENTS movement of the pressure plate, and the full condition 3 229 618 H1966 (305mm 6 5 of the compaction chamber. time delay circuit auto- 2 3,353,478 1 m Hopkins loo/52 matically shuts down the machine when any of the op- 3:539:74l 11/1970 Volandf: erational cycles continues beyond a predetermined 7 3,606,830 9/1971 Chaney... 100/5'2 limlt- 3,627,959 l2/l97l Chapell..; 200/6L62 3,762,312 1011973 Guhl.. 100152 a 4 C GYDraWmg Fgures Pmmmnscwm w www w CONTROL SYSTEM FOR A COMPACTING MACHINE DESCRIPTION OF THE INVENTION popular for reducing the volume of paper waste and other useful but bulky commodities, as well as for the crushing of refuse in both home and commercial environments. The rapdily expanding usage of such machines has compounded the-incidenceof injury resulting from the inherent dangers attendant, tothe operation of the power-assisted compaction process. Conventional compaction machines have employed few,if any, safety'features'beyond the usual safety interlock on the door tothe compaction chamber.
It is a general object of the present invention to provide a control for a compacting machine which provides a degree .of safety to the operator which has heretofore been unavailable in such machines. More specifically, it is an object of the present invention to provide a control system for a compaction machine which includes a non-defeatable door interlock and which provides for theoperator visual indicationsof the operating condition of the machine so as to minimize the possibility of injury resulting from, operator mistake in using the machine.
lt is a more specific object of the present invention to provide a control system for a compacting machine whi'chgivesvisual indications of the operating or ON condition of the machine, the direction of movement of the pressure plate andthe full condition of the compaction chamber. t v
- 'Yet'another object of the present invention is to provide a control system'which protects the operator and i v the machine in the event ofla malfunction which causes any operational cycle of the ma'chine'to continue for an I excessively long time period. A related object of the invention is-to provide forautomatically shutting down the machine when-any of the operational cycles continu'es byond a normal time period.
Prior compaction machines have also been devised for operation in a baling mode, in which the'contents of the compaction chamber are held in a compressed state for manual binding by the operator. However, the
known machines useful for this purpose have required that the operator continually monitor the operation of the pressure plate and manually, shut down the machine at or near the point of maximum compaction pressure.
provide a control system which senses the condition of maximum compaction pressure during the baling operation and automatically holds the compaction chamber. contents in a compressed maximum-pressure state so as tofacilitate baling A still further object of thepresent invention is the provision of a control system which provides repetitive tamping of the chamber contents during each operational cycle of the machine as-the chamber volume reverse directions'through the compaction chamber reaches the full level, thus creating a tightly compacted bundle. Other objects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to. thedrawings, in which: I
FIG. 1 is an elevational view of a compaction machine embodying a'contr'ol system constructed in accordance with the present invention; v FIGS. 2a -2 c, when taken together, constitute a schematic diagram of the electrical circuit used in the control system of the present invention. v
FIGS. 3a-3b are exploded detail views. of a limit switch-arrangement. t i
While the invention will be described in connection with preferred embodiment, it willbe understood that placed in the lower section of the compaction compartment 12 for receiving the material to be compacted, removal of the box 20 being facilitated by an ejection strap 22 which generally lies behind and under (from the operators standpoint) the box 20. At the lower end of the ejection strap 22 is a handle-24 through which the operators hand may be inserted during ejection of the.box 20. 'At a point above the level of the box 20 there is provided'in the door I6' an'a pertur e '26 normally covered by a hinged door 28 which, when opened, forms-a chute through the door 16 into the box 1 During norma lserviceas a'compacting machine, the material to be compacted is inserted into the'closed chamber 12 through the chute formed in the aperture 26 of the door 16. For compressing the contents of the chamber '12 a pressure plate 30 is provided which of such a size as to substantially span the horizontal area of the chamber 12 and, in particular, the horizontal area of the box 20. The plate 30 is guided by a pair of vertically extending guide bars 32, 34 extending upward into the control chamber 14.
For moving the pressure plate 30 in the forward and 12, there is provided a' reversible drive souce in the form of a motor and hydraulic pump, indicated generally at 40, which positions a hydraulic ram 42 which n runs downward through the machine into engagement at itslower end with the pressure plate 30. Areservoir 46 provides hydraulic fluid for the motor 40.
Although many different drive sources could be employed with the present invention, a particularly suit- I able drive source, and the oneenvisioned in the following description, includes a two-stage double pump having a solenoid-controlleddirectional valve which'is ac-' tuable to change the directionof motor force on the hydraulic ram 42. The pump is driven by an electrical motor selectively controlled by an electrical .relay in a ,manner hereinafter described. Also housed inthe chamber 14 is a control circuit module 50 having a of indicators and sides of the power line have switches 62, 64 connected in series therewith and controlled manually by a front panel key-locked actuator 66. The motor 68 of the hydraulic motor and pump unit 40 is selectively connected across the switched side of the 120 volt line by a normally opened contact set 70 of the drive motor relay 72. Similarly, a drive solenoid 74 for the directional valve of the motor and pump unit 40 is connected in series across the switched 120 volt line through a pair of normally opened contacts 76 of the directional hydraulic valve relay 78.
control circuit of the dc. operating power whenever the doors 16, 28tothe cabinet'are open. To this end, a magnetically actuated switch 130 is provided in series vwith the dc. supply output 114 and the operate lamp a For converting the a.'c. electrical inputpower into a plurality of do. electrical voltages for usein the control circuit, there is provided a power supply module, indicatedgenerally at 80, including a principal supply transformer 82 having a primary winding 84 one half of which is connected in series with. the switched supply lines through a protection fuse 86. A neon lamp 88 in series with a current limiting resistor 89 is also connected across the same half of the primary winding 84 to provide a visual indication of the presence of 120 volt a.c. input voltage to the power supply-module 80, and is located on the power supply module 80. A secondary winding 90 of the split type is center tapped to provide a ground line 92 and, operating in conjunction with a pair of rectifier diodes.94, 96 forms part of a conventionalfull-wave rectifier commonly used in the power supply art. The outputfrom the rectifier is applied across a smoothing capacitor 98 which, to a large degree, removes the ripple from the rectified signal and 7 provides a first dc. voltage on asupply output line 110 which is applied to one side of both the motor drive relay 72 and the directional hydraulic vavle relay 78. The output line 110 also provides power for the pressure plate direction indicator lights 246, 300and the full condition lamp 440 in a manner hereinafter described.
A sec ondand lower d.cl supply. voltage is provided on an output line 114, which is connected to the power line 110 through a dropping resistor 116 and is further regulated by a smoothing network consisting of a capacitor 118 and resistors 119, 120. The dc. supply line 114 provides a low level d.c. signal, typically -l2 volts, for the small-signal switching circuits hereinafter described. 7
In accordance with one aspect of the present inven- 126, the series circuit further including an operatind diode 132 between the magnetic switch 130 and the lamp 126. A permanent magnet 134 is installed in the chute door 28 (FIG.- 1) and is operative to close the contact of the switch 130 whenever the doors 16, 28
,are both closed at the'same time so as to. bring the magnet 134 into proximity with a detecting pickup 136 located on the side panel 10. An indication of the closed condition of the two doors 16, 28 is provided by the lamp 126, which is illuminated to a high brilliance by current flowing through themagne-tic switch 130 and diode 132 from the dc. supply line 114.
The control system of the present invention can be broadly characterized in terms of its principal modes of operation, which .are briefly set forth here and described in detail ina later section of the specification.
First, one of the principal modes of operation is the compaction or PACK function, in which the pressure plate 30 moves from its uppermost orRETURN position down through the chamber 12 to compact the material previously inserted therein, followed by the automatic return of the pressure plate 30 to its uppermost position. To this end, the control system provides means responsive to a packing initiation signaland-operatively associatedwith the reversible drive source to additional means respond to this output signal from thesensing means to reverse thedirection of operation of tion, an output indication is provided whenever the main key-operated power switch 66 is actuated. To this end, a third output from the power supply module 80 is provided on an output line 122, which is connected to the output'line 114 through a dropping resistor 124. An indicator light 126 is provided on'thejfront panel of the module and is connected to the output 122. Sufficient current is drawn through the dropping resistor 124 to actuate the light 126 to a low but visible level of illumination indicating that the operating switch. 66 is on but that at least one of the doors 16, 28 to the cabinet is not'closed.
A related featureof the invention lies in the provision .of a magnetic interlock switch which cannot be defeated by normal techniques and which deprives the the drive source so as to retractthe pressure plate 30. Finally, position responsive means renders the drive source inoperative on the achievement of the fully retracted position'of the pressure plate 30. v
It is usually unnecessary for the top panel ll of the compaction chamber 12 to beresisfiiift fihecompaction pressure normallyattained in the chambe'r l2inasmuch as these pressures are exerted downwardly on the side walls and bottom of the chamber by the pressure plate 30. For this reason the top panel 11 of the compression chamber is usually formed of relatively lightwight material and is not adapted to withstand high pressures. Under these circumstances it is possible, however, that some refuse being compressed, may inadvertently bypass the pressure plate 30 during downward travel of the plate in the chamber, withj'the result that some suchmaterial ends up on top of the pressure plate. Another way'in which this could occur would be if the operator inadvertently admitted refuse to be I compacted into the chamber 12 when the pressure plate 30 was in some position other than its uppermost position.
Forthe purpose of detecting the presence of any refuse being compacted on top of the pressure plate 30 soon enough to prevent damage to the top panel 11 of the'chamber 12, a limitswitch arrangement 31 is provided, as shown in FIGS. 3a and 3b. The limitswitch arrangement. 31 includes a vertically disposed rod 33 which is slidably mounted to the frame 35 of the compaction machine by means of a pair of vertically spaced pillow blocks 37 and 39. The lower end of the rod 33 is arranged to extend downwardly. slightly into the compaction chamber 12 when the'pressure plate 30 is. not in its uppermost position (see- FlGp3b). when the pressure plate moveslupwardlyin thechamber 12 toward its uppermost position, itapproaches and engages the lower end of the rod 33 and accordingly forces the rod upwardly. Means in the form of, a collar 41 provided near the upper end of the rod 33 is provided for terminating upward movement of the-pressurelplate 30'when the plate is invits uppermost position by tripping the switch 164 also mounted on the frame 35 of the inachine (see also FlGrl Akeeper'collar 43-is also provided on the rod 33 to hold the rod in place during repair if necessary, and other collar 45 mounted near the lower end of the rod 33 limits the downward movement of the rod into the compression chamber 12 by engagernent with the top panel 11; The rod 33 is biased by means of a coil spring 47Idisposed between ,the 'upper spring normally urging the rod downwardly so that the lower collar 45 is disposed, against the top panel 11 of the compaction chamber l2.
Thus it is seenthat the'pres'sure plate 30 moves upwardly within the chamber 1 2, if any refuse is inadvertently present in the'space between the pressure'plate and the top panel 11 of the compaction chamber, the
limit switch arrangement .31 will function to terminate upward movement of the pressure plate (via the collar 41 and switch-l64);before compaction of the refuse serted. lf,:however, after the second compaction the volume remains above the full leveLthe operator is signaled with a visual indicating light that the chamber 12 is full, indicating'that thel'contents should be removed before further compacting isattempted To this end, the apparatus described above furtherincludes a volume sensing'deviceproviding an in'dicatiohflthatthe value. The output signal generatedin response tothis maximum pressure condition acts'u'pon means associated with the drive source to stop-the forward advancement of the pressure plate 30 and hold the contents of the chamber 12 at the predetermined threshold pressure. Finally, means are provided for reversing the operation of the' drive source in response to a inanual initiation by the operator so as to. retract the pressure plate 30 and allow removal of the compressed contents.
Various other features of the presentinvention, such .as the automatic shut-off safety feature, will become apparent from'the following detailed description of the circuits of FIGS. 2a-2c. t
' Returning then to FIG. 20, there is-showna manual mode selector switch 140 of the momentary contact type with contacts 142 through 146 and spring biased to acentral OFF -position. The contact 14l'is electri- 1 cally connected directly to the outputline 114 from the pillow block 37-a'nd the switch'actuating collar 41, the
compressed volume is less than a predetermined threshold volume and a time delay device associated with the aforementioned pressure and volume sensing devices and operative to begin a timed period when ever the output signal from the pressure sensing device occurs before the compressed volume falls below the predetermined threshold volume. Finally, there is proto reverse the direction of thedrivesource so as to cause a second compression of the contents of the chamber 12:. After'this occurs additional means are provided for illuminating the full condition indicator lamp 440. if, a second compression having occurred, the output signal from the pressure sensing means again occurs before the compressed volume hasfallen below the predetermined threshold volume.
Third, the control system ofthe present invention provides an automatic 'balingfunction. In the BALE mode, the pressure plate 30 responds to a baling initia-,
tion signal to advance through the chamber 12 until the pressure of the contents of the chamber 12 against the vided means responsive to the end of the timed interval dic. supply 80, while the contacts 143,. are connected torthe same outputline' 114 through the magnetic door interlock switch 130. The switch 140 is a threeposition switch having, inaddition to the OFF position. BALE and PACK-RETURN positions. Three principal output terminals 148, 150,152- are controlled by the;switch 140 and provide the primary function ini- 'tiating signals for the control system. Specifically, during normal-operation the terminal 148: is high (apositive dc. voltage) whenever' the mode selector switch, 140 is in the OFF or BALE positions and low whenever theswitch 140 is in the PACK-RETURN position, That is, the contacts 141', 1.42 are normally closed whenever switch 140 isin the OFF or BALE position and normally open .whenever switch 140 is .in the PAC K RETURN position. The terminals 150, 152 are supplied by the dc. supply output line 114 when the mode selector switch 140 is respectively in the BALE and PACK RETURN positions, assuming that the doors 1 6,
' 28,'and hence the magnetic switchl30,, are closed. I
That is, the;.contacts 143 through 146 are normally open. The contacts 143, 144 are closed only when the switch 140 is in the BALE positionand the contacts 145, 146 are closedonly when the switch 140 is in the PACK-RETURN position, At all other times, the terminals 150,'152 are electrically isolated. As such, the 1 switch 140 mayv be manually engaged to providea packing initiation signal on the terminal 152 or -a baling initiation signal on the terminal 150.
For the purpose of sensing when the resistance pressure of the contents of the chamber 12 against the pressure plate 30 reaches a predetermined threshold value,
there is provided a pressure sensingswitch of the single-pole double-throw type having its common pole connected to the interlocked output of the power. supply 80 through a dropping resistor 162 and a normallyclosedswitch 164. The details of the pressure switch 160 are within the knowledge of those skilled in the art and need not be set forth here. Suffice it to say that the contact arm of the switch 160 normally assumes the lower.(shown) position when the pressure is below threshold and is actuated to the upper position when the pressure is above threshold. The switch 160'may be responsive to mechanical stress on the pressure plate 30 or chamber 12 forv instance. Preferably, however,
, the switch 160 is hydraulically actuated-and is responpressure plate 30- reaches a predetermined threshold sive to the build-up of'pressure fluid behindthe hydraulic ram 42. In its-lower position, the switch 160' norother times.
mally provides a positive supply signal to aterminal 166 which controls driving down of the pressure plate or return position. Therefore, during operation of v the compaction unit, the switch 164 is closed to provide a holding signal (the significance of which will become clear) at a terminal 170 and a dc. input signal to the pressure switch 160. p
A second pressure plate position sensing switch 172, hereinafter called the low limit switch, is connected in series with the normally open contact of the pressure switch 160 and operates in conjunction with the switch 160 to provide a positive dc. voltage of the terminal 174 whenever the contents of the chamber 12 exceed a predetermined full level at' the end of the downward motion of the pressure plate 30. Specifically, the switch 172- is closed whenever the-pressure plate 30 is above the full .level and open when the plate 30 is below the full level. Therefore, a full condition indicating signal is produced at terminal 174 only if the pressure plate 30 encounters the threshold resistance pressure while at a position-above the low limit threshold level.
Turning now to FlGS. 2b and 20, it is seen that'the terminals to the left of these FlGS. correspond in numher to the terminals to the right of FIG. 2a,- and for clar- 8. resistor 202 and a base-emitter bias network consisting of resistors'204, 206. The junction of the'resistors 204, 206 receives a drive signal from the cathode of the SCR 184. The transistor 200 is referenced to ground potential through the emitter resistor 202 and has its collecj tor connected to one terminal of the motor drive relay solenoid 72through the connecting terminal 208.
It should be notedat this point that the energization of the motor drive relay solenoid '72 (FIG. 2a) initiates movement of the pressure plate 30 in one direction or the other, depending on the condition of energization of the directional valve solenoid 78. The directional 212 consisting ofa transistor 2140f the NPN type'having its emitter referenced toground through a resistor 216 and its base biased by a network consisting of resis-' .tors 218, 220. The collector of the transistor 214 is connected to the control terminal of the directionalvalve solenoid 78 through a terminal connector 222.
' When rendered conductive, the. transistor 214 is operaity, are provided with functional designations providing ease of description. The reader is cautioned not to assume that all. signals necessarily flow from'left to right, since the reverse is often true, particularly in the instance of the hold terminal 170 and the lower six terminals hereinafter described; I lt will be recalled that the initiation signals provided at't he terminals'l50, 152 for the BALE and PACK- RETURN functions are momentary. For the purpose of providing a memory during the respective BALE and PACK-RETURN operations, there is provided a balememory, circuit :180 anda pack memory circuit 182 I which are similar, butnot identicalin operation. The
bale memory circuit 180 assumes a first state during the entire bale cycle and a second state at all other times. The pack memory 182 assumes a first state during the entire pack or return cycles and a second state at all Taking the pack memory 182 first, it is seen that the circuit is principally composed of a silicon controlledrectifier (SCR) 184 having its anode supplied by a hold line 171 connected to the hold terminal 170 and its cathode terminal connected to, among other things, a motor relay drive circuit 186. The gate terminal of the SCR- 184 receives its trigger signal from the packinitiation signal at the terminal 152 through an RC decoupling network 188, a blocking diode 190 and a resistor The motor relay driver circuit 186 includes a switching transistor 200 of the NPN type. an emitter dropping tive to energize the solenoid 78. I
The down relay driver circuit 212 is initially rendered conductive by either the bale initiate pulse at. terminal 150 or the pack initiate pulseat terminal 152. Specifcally, the bale initiate pulse reaches the relay drive through an R-C decoupling circuit 226, a directional diode 228 poled to conduct current toward thetransistor 214 and a pair of series resistors230, 231, the latter of which supplies current to the junction of the resistors 218, 220 to bias the transistor 214 into conduction.
The pack initiation signal at the terminal '152 simi larly beginsconductionin the driver transistor 2 14 by providingcurrent to the transistor through.aidirectional diode 236 and the aforementionednetwork consisting of the series resistors 230, 23l,and the bias network consisting of the resistors 218, 220.
connected to the bias resistors 218, 220 of .the directional solenoid' driver circuit 212 and its gate terminal connected to the junction of the bias resistors 230, 231, 394. Anode current for the SCR 242 is normally provided from the power supply through the normally closed (lower position) terminal of the pressure switch 160, the drive-down terminalconnector 166 and an R-C decoupling network 244. i
While the relay driver circuit 212 is held in conduction by the conducting SCR 2420f the drive down 0 memory circuit 240, a visual indication of downwardtor lamp 246-on the front panel 50 (FIG. 1 and FIG. v
2a). As in the case of the down direction solenoid 78,
travel of'the pressure plate 30 .is provided by an indicasustaining current for. the down direction indicating light 246 is primarily provided by the drive down memory circuit240. To this end, there is additionally provided a down lamp driver circuit 250 which includes a transistor 2520f the NPN type having its emitter couthebale memory circuit 180.
pled to ground through a resistor 254, its collector coupled to the down lamp 246'thoru gh a connector terminal 256 and its base terminal connected to the cathode of, the SCR 242 through a directional diode 258 in series with an input resistor-260. Qui te clearly, the SCR 242, when rendered conductive, simultaneously provides drive current to the down relay driver circuit 212 and the down lamp driver circuit 250 so as to cause energization of the directionalsolenoid 78 and illumina- Thebale memory circuit 180 includes a silicon controlled rectifier 266 and'a gate terminal bias network consisting of resistors 268, 280. Holding current for the anode terminal of the SCR 266 'is normally-provided with a description of from the power supply '80 through the normally closed (lower) contacts of the pressure switch l60.via the drive-down connector terminal 166 and the R-C' decoupling network 244. Current from the cathode of the SCR 26 6.is coupled through a directional diode 282 to a connection 284 withthe cathode terminal of the pack memory SCR 184 from whichpointthe drive current for the motor, relay driver circuit 186 is derived. Finally, the gate terminal of the SCR 266 in the bale memory circuit 180 receives its trigger signal in response to the occurrence of a bale initiation pulse at the terminal 150, current being routed to the gate terminal of the SCR-266 through the R-C decoupling net work 266, a direction diode 290 and the bias resistor 268. l
A brief description of: the operation of the circuit described thusfar will facilitate further analysis of the system as a whole. Before initiation of either of the principal functions, the system is in a quiescent condition in which the pressure plate 30 is at its uppermost position. I
The high limit switch 164 is openso that the dc. supply voltage is not present'at terminals 166, 170,174 in which case the pack'memory circuit 182' and the bale memory circuit180 are inactive or non-conductive.
Manual operation of the function selector switch 140 I to the PACK-RETURN position causes a pack initiation pulse to be routed from the power supply 80 to the .pack connector terminal 152. Anode circuit for the pack memory SCR 184 momentarily flows through the directional diode 19 8 from the R-C decoupling, network-188, while gate current for the sameSCR 184 is provided through the diode 190 and resistor 192. The SCR 184beginscon'ducting and, via its'cathode current, renders the motor relay driver circuit 186 conduca 10 rent frorn'the pack terminal 152 through the directional diode 236 and resistor 230. The SCR242 begins conduction. The gate signal for the SCR 242 is also applied to thedown relay driver circuit 212 through the resistor 231 so as -to initiate conduction in the transistor 214 to energize the directional-valve solenoid 78 so that the pressure plate 30 begins movement in a downward direction. I I i As the pressure plate 30 leaves its'rest position, the
high limit switch 164 (FIG. 2a) closes to replace the pack initiation signal as a source of drive current for the hold'terminal 170,-which supplies the anode of the pack memory SCR 184, and the drive down terminal 166 which supplies the anode current for the drive down memory SCR 242. I v
The pressure plate 30 continues its downward travel, with the drive-down memory circuit 240 hold the down lamp driver circuit 250 and the down relay driver circuit 212 in conduction.
Initiation of'the BALE function by movement of the mode selector switch to the BALE position produces a similar result, since both the bale andpack functions have a common start. The bale initiation pulse at the terminal activates the balememory circuit .180 'by simultaneously providing a signal to the gate of the SCR 266 (through the R-C network 226, the
diode 290 and resistor 268) and to-the anodethereof down memory SCR'242 is connected to the anode of the bale memory SCR 266 and is supplied simultaneously therewith-while the gate voltage for the SCR 242is supplied from the bale terminal 150 through-the R-C network 226, the diode 228 and resistor 230. Con- I f duction through the down relay driver circuit 212 is ini-' tiated by the bale initiate pulse appearing at the gate of the drive down memory SCR 242,--and conduction in both'the down relay. driver circuit 2l 2and the down lar np'driver circuit 250 is sustained by "conduction through the drive-down memory SCR 242.
In additionto the down direction lamp 246, there provided an up direction lamp 300 for indicating to the operator the condition of upward travel of the pressure plate 30. The lamp'300 is controlledby an up lamp driver. circuit 302 consisting of a transistor 304 of the NPN type having its emitter coupled to ground through i a resistor 306 and its collector connected to the control terminal of the lamp300thr oughthe up lamp drive connector terminal 308. Conduction through the transistor 304, and hence illumination of the up lamp 300,
is normally controlled by the conduction state of the pack memory SCR 184 asa result of theconnection of i the cathode of the SCR 184 to the base of the transistor 304 through a pair' of input resistors 310, 3 12. However, it isdesirable to inhibit operation'of the up lamp driver transistor 304 and the lamp 300 when the pack memory SCR 184 is in conduction if the pressure plate 30 is moving in the down direction. To this end, there is provided a second transistor 314 of the NPN type which is shunted across the base-emitter circuit of the transistor 304; and controlled from the cathode of the drive memory SCR 242 via a base resistor3l6. The emitter of the up lamp driver inhibit transistor 314 is referenced to ground through an emitter resistor 318.
-Whenever the drive down memory SCR 242 is conducting, the inhibiting transistor 314 is similarly con as a result of initiation of this function. Upward movement of the pressure plate 30 does not automatically occur asa result of initiation of the baling function. Therefore, itis necessary for the operator to manually engage. the mode selector switch l40.and turn it to the PACK-RETURN position at the end of the baling function in order to begin the upward movement of the pressure plate 30.
Returning to the operational description of the packing function, the pressure plate 30 travels down through the chamber 12 and compresses the contents thereof until the predetermined threshold pressure (approximately 2,000lbs. in an actual application) is reached. At this point the contact arm of thepressure switch 160 moves from'its normally closed position to an open position (upward in FIG. 2a which causes supply voltage to be removedfr'om the drive down terminal 166 and hencefrom the anode of the drive down memory SCR 242. Conduction in the down relay driver circuit 212and the down lamp driver circuit 250 stops, causing deenergization of the directional valve solenoid 78 and extinguishing the down indicator light 246 on the operators panel 50. The up lamp driver circuit 302 immediately becomes conductive to illuminate the up direction lamp 300 as the inhibiting transistor 314 is rendered non-conductive along with the drive down memory SCR 242.
Deenergization of the directional valve solenoid. 78 allows the directional valve to return to its normal condition which causes the pressure plate 30 to be driven in the upward direction. Since the motor relay driver Circuit 186, and the-motor drive solenoid 72 are held closed terminal so as to remove-the d.c. supply voltage from the drive down connector terminal 166; During the downward operation of the pressure plate 30 in the BALE mode, the bale memory circuit 180, the motor relay driver 186, the drive-down memory 240, the down-relay driver circuit 212, and the down lamp driver circuit 250 are conductive. However, removal-of the dc. supply voltage from the drive down connector terminal l66 deactivates the bale memory circuit 180 by depriving the SCR 266 of its anode current and simultaneously deactivates the drive-down memory circuit 240 by depriving the SCR 242 of its anode current. Deactivation of the bale memory circuit 180 terminates the drive current to the motor relay driver 186, while deactivation of the drive-down memory circuit 240 terminates the input current to the down relay driver circuit 212 rendering this circuit inoperative so as to leave the pressure plate 30 in its lower position to hold'the contents of the chamber 12 at the threshold compres sion pressure. The door 16 to the chamber l2 may then be opened to allow the operator to tie the compressed bundle. y The function of the down lamp memory circuit 320 is to provide a visual signal to the operator of the position of the pressure plate when the bale cycle is completed. The bale cycle terminates when thecomin conduction by the conductive condition of. the pack memory SCR 184, the pressure plate 30 automatically reverts from travel in the downward direction to travel in the upward direction toward a-position of full retraction from the contents of the chamber 12.21130, since the pack memory SCR 184 remains in conduction, the up lamp driver circuit 302 remains in conduction to give a vis ual indication to the operator of the direction of movement of the pressure plate 30.
The pressure plate 30 movesupward through the chamber 12 to the retracted position at which point it comes in contact with the actuator for the high limit switch 164, opening the switch 164 and disconnecting the dc. power supply from the hold terminal 170, and hence depriving the pack memory SCR 184 of its anode current'As the pack memory SCR 184 ceases conduction, drive current for the motorrelay driver ,186 disappears and the pump motor drive solenoid 72 is de energized. The pump stops and the machine re mains in a quiet condition until a further operation is initiated. Also, as the pack memory SCR 184 ceases conduction, drive current for the up lamp driver traneventually encounters resistance equal to the threshold pressure of the switch 160, causing the contact arm of the switch 160 to move upward from its normally mum compression pressure-of the pressure plate 30. When the machine is in this .state,'the d.c.supplyvo1tage to the pressure hold down terminal 166 is removed by the opening of the compression pressure switch 160. Thus, the drive down memory SCR 242 is deprived of anode voltage and ceases conduction. At this point, the down lamp driver transistor 252 would also cease to conduct and the'down lamp 246 would be extinguished if an alternate source ofdrive for the down lamp. driver transistor 252j'was not provided. It is the function of the 1 down lamp memory circuit 320 toprovide this alternate drive source, thereby enabling the operator to re ceive a visual output of the position of the pressure plate 30 while the cycle and idle. I g
Specifically,; the down lamp memory circuit 320 is principally composed of a SCR 322 having its anode terminal supplied by the off terminal 143through an R-C decoupling network 324 and its cathode terminal connected to 'the'base of the down lamp driving transistor 252 through a resistor 326. The cathode terminal of the SCR 322 is also referenced to ground through a resistor 328. The gate terminal of the SCR 322 receives its trigger signal from the'bale initiationterminal 150 through'an 'R-C decoupling network 226, a blockingdiode 328 and a bias-resistor 330. An additional bias resistor 332 connects the gate and cathode terminals. Thus, the SCR 322 begins conduction whenever its gate terminal receives a bale initiation signal from the manual mode selector switch through thebale initiation terminal and ceases conduction only when its anode terminal current is interrupted by turning the manual mode selector switch 140 to the PACK- RETURN position. f g
It will be recalled from the prior description that the contacts 141, 142 of the manual mode selector switch 140 are normally closed in the OFF and BALE positions and normally open in the PACK-RETURN'position. Thus, the SCR 322 of the down lamp memory circuit 320 and the down lamp driving transistor 252 are machine 'is' the completed bale r 13 in conduction and the downlamp 246 remains illuminated after maximum compression-pressure of the pressure plate 30 is achieved. Only when the. operator subsequently generates a pack initiate signal by turning the manual mode selector switch 140 to the PACK- RETURN position are these circuits 320, 250 deenergized and the down lamp 246 extinguished. s
The functioning ofthe return logic circuitry 450 will be discussed below. Suffice it to say at this time that the operator has the capability, after the'compressed material has been bound and thecompaction chamber doors 16, 28 have been closed thereby activating themagnetically actuated switch 130, to cause retraction of the pressure plate 30 to its uppermost position by turning the manual mode selector switch 140 to the PACK- RETURN position. The compaction chamber door 16 may then be reopened'to allow removal of the compressed bundle. i
Note that the magnetically actuated switch 130 re quires that both compaction chamber doors 716, 28 be closed before any movement of the pressure plate 30 can be initiated or sustained. That is, if the magnetically actuated'switch 130 is-open, the manual mode sele'ctor switch 140 is disabled from sending any pressure plate 30 initiating'signa'ls to the bale initiate terminal 150 or the pack initiate terminal 152. Also, if the pres: sure plate 30 is in motion, opening of either of the compaction chamber door 16,28 also opens the magnetically actuated switch 130, thereby depriving the hold terminal l70 ,'the pressure plate drive down terminal 166, the pack memory ci'rcuit'l 82, the bale memory circuit 180 and the motor relay drive circuit 186 of supply voltage. Thus an'y movement of'the'pressure plate 30 immediately ceases upon'opening of either compac-, tion chamber door 16,28. Therefore, it is possible for the operator to remove the compressed bundle without any interference from or injury caused by movement of thepressure plate 30. A
' Turning now to the, tamping function, it'will be reealled that this function occurs whenever the volume of the compaction chamber 12 approaches a predetermined full level. This function generates a second compaction' cycle if the firstcompaction cycle fails to corn 1 1 1'4 SCR 342. The sea 342 begins conduction when a positivepulse at the full "condition terminal 174 is conducted through the RC decoupling network 350, the
directional diode 344 and the biasresistor 346 to the gate terminal of the SCR 342. The full condition pulse is generated atlthe full condition terminal 174 whenever the pressure plate 30 moves from its uppermost rest position, thereby closing the" normally open contacts of the high limit switch 164, and reaches the threshold compression pressure of the pressure switch 160 before the'pressure plate 30 advances to the predetermined full level of the compaction chamber 12-. The low limit switch 172, which is normally closed, is mechanically actuated to an open condition whenever the pressure plate 30 advances to a position below the'predetermined full level. i
The details of mechanical actuators for level sensing switches, such as the low limit switch 172, arewithin the knowledge of those skilled in the art and need .not be set forth here. Thus,- anytime that the machine com pacts its contents to the point where the pressure. plate 30 is above the full level .when the maximum compaction pressure is achieved, a full'condition pulse is generated at the full condition terminal 174. When the full condition pulse is applied to the gate terminal of .the full memory SCR 342, the SCR 342beg'ins conduction and supplies operating voltage to the tamp pulse generator circuit'360. I v
The tamp pulse generator circuit 360 is principally composed of a programmable unijunction transistor press the volume of the compaction chamber 12 belo the full level. lf the second compaction cycle compresses the volume below the full level, additional ma- ,terial may be inserted. However, if the volume remains above the full level after the second compaction cycle, the operatoris visually signaled that the compaction chamber 12 is full, indicating that the contents of the chamber 12 should be removed before attempting further compacting. Specifically, the full memory circuit 340, the tamp pulse generator 360, the tampmemory 380, the full lamp memory .400, the full lamp flasher circuit410 and the full lamp driver circuit 430 accomplish these functions in the mannerhereinafter de-" scribed;v r
The full memory circuit 340 is principally composed of an SCR 342 having its'anode terminal supplied by the dc. supply line at the terminal 148 through the'R-C decouplingv network 324-and its cathode terminal .con-
'ne'cted to the bias resistors 364, 366, 3700f the tamp (PUT) 362 having its gate terminal connected .to-the voltage reference resistors 370, 372, with-the'resistor 370 connected to the 'cathode'terminal of the SCR 342- and-the resistor 3752 reference to ground. The anode of the PUT 362 is-connected to the timing resistor366- and the timing capacitor 368, with the timing resistor 366 also connected to the cathode terminal of the SCR 342 and the timing capacitor'368 reference to ground. The load resistor 364 provides a sufficient load to the full memory SCR 342 to ensure'that-the SCR 342 remains in conduction and is connected between' the cathode terminal of the SCR 342 and ground. The
cathode terminal of the PUT 362 is referenced to ground through the resistor 374 and is connected to the tamp-memory SCR 382 through the gate terminal biasing resistors 376, '384.
The function ofthe tamp pulse generator circuit 360 is to provide a pulse to the tamp memory circuit 380 which'is delayed in time with respect to-the initiation.
of conduction in the full memory SCR 342. When the SCR 342 begins conduction, a voltage reference is im-' mediately established on the gate terminal of the PUT 362 by the voltage reference resistors 37.0, 372. The voltage of the timing capacitor 368 begins to rise as it is charged through" the timing resistor 366. When the voltage on the timing capacitor 368, and hence that on the anode terminal of the PUT 362, reaches thev voltage reference at the gate terminal of the PUT 362,, the PUT 362 istriggered into conduction and'the charge on the timing capacitor is discharged through the PUT cathode terminal to generate a positive pulse to the gate biasing resistors 376, 384 of the tamp memory'SCR 382.
The delay time of thepulse is directlyproportional to the-value of the timing resistor 366 and the tiniing capacitor 368, the, values being selected to produce a delay time of a few seconds, e.g.-, 5 seconds.
The tamp memorycircuit 380 is principally composed of an SCR 382 having its anode connected to the dc. supply through the off terminal 148 and the R-C decoupling network 324 and its gate terminal connected to the biasing resistors 376, 384. The cathode terminal of the tamp memorySCR 382 is referenced to ground through the resistor 386 and is also connected to the anode of the full lamp memory SCR 402 and to the differentiating capacitor 388. The other terminal of the differentiating capacitor 7 388 is referenced to ground through the resistor 390 and is.connected to the gate of the drive down memory SCR 242 through the directional diode 392 and the resistor 394.
The function of the tamp memory circuit 380 is to provide d.c. supply voltage to the anode of the full lamp memory SCR 402 and to provide a trigger pulse tothe gate of the drive down memory SCR 242. When the circuit 380.
The full'lamp memory circuit 400 is primarily coinposed of an SCR 402 having its anode terminal connected to the cathode terminal of the tamp memory 'SCR 382 and its cathode terminal connected to the resistors 414, 418, 422 of the full lamp flasher circuit 410. The gate terminal of the SCR 402 is connected to the full condition terminal 174 through the RC coupling network 0, the directional diode 404 and the bias resistor 406. An additional bias resistor 408 com nects the gate and cathode terminals of the SCR 402.
' The. function of the full lamp memory circuit 400 is to provide d.c. sup'ply voltage to the full lamp flasher the gate terminal of the full lamp memory SCR402 through the R-C decoupling network 350, the directional diode 404 andthe bias resistor 406. Since the anode terminal of the SCR 402 had d.c. supply voltage applied by the conduction of the tamp memory SCR 382, the SCR 402 is nowtriggered into conduction. Note that if the tamping function is successful in compressing the contents of the compaction chamber 12 to a. point below the full level, a full condition pulse is not generated at the full conditionterminal 174 at the end of the tamping cycle because the low limit switch 172 opens whenever the pressure plate 30 advances to a point below the full level. Thus, the full lamp memory SCR 402 is triggered into conduction only if the tamping operation isunsu'ccessful in compacting the material in the compaction chamber 12 to a point below the full level.
The full lamp flasher circuit 410' consists primarily of a programmable unijunction transistor (PUT) 412 having its gate terminal connected. to a pair ofvoltage reference resistors 414, 416 and its anode is connected to a timing resistor 418, a timing capacitor 420 and the full lamp driver'resistor 436. The timing resistor 418 is referenced to the dc. supply voltage provided by the full lamp memory SCR 402 and. the timing capacitor 420 is referenced to ground. The loadresistor 421 ensures that sufficient load is provided'to the full load memory SCR 402 to sustain its conduction. The cathode of the PUT 412 is connected to a discharge resistor .422 which is referencedto ground. When the full lamp memory SCR 402 begins conductiomthe voltage reference resistors 414, 416 immediately establish a voltage reference at the gate terminal of the PUT 412. The timing capacitor 420- begins to charge through-the timing resistor 418. when the timing capacitor voltage, and hence the voltage at the anode terminal of the PUT 412, reaches the voltage reference established at the gate terminal of the PUT 412, the PUT 412 is triggered into conduction, dischargingthe timing capacitor 420 through the cathode terminal of the PUT 412 and they resistor 422. The charging and discharging of the timing capacitor 420 continue as long as the full lamp memory SCR 402 provides d.c. supply voltage. Thus, the output to the full lamp'driver circuit 430 is a sawtooth waveform andthe full lamp'flasher circuit 410 functions as a sawtooth oscillator. The period of the sawtooth waveform is dependent upon vand directly, proportional to the selected values of the timing resistor 418 and the timing capacitor 420,- the values being selected to produce a waveform period of less "than about'l second, e.g., about second.
The full lamp circuit consists primarily of a Darlington connection of two transistors 432, 434 of the NPN type with theircollector terminals connected to the full lamp 440 through thefull lamp terminals 438.,The emitter terminal of the transistor 432 is connected to.
the base terminal of the transistor 434 and the emitter of the transistor" 434 is referenced to ground through the resistor 442. The base terminal of the transistor 432 is connected to the timing capacitor 420 and the anode terminal of the PUT 412 through the'resistor 436. The sawtooth waveform'from the full lamp flasher circuit 410 alternately drives the full lamp driver transistor 432, 434 into and out of conduction. The on-and off switching of the full lamp driver transistors 432, 434 causes the full lamp 440 to flash, creating a more noticeable and visible warning indicator to the operator that the contents of the compaction chamber 12 should be removed The full lamp 440 will continue to flash on and off until the anode terminal voltage of the tamp memory SCR 382 removed Specifically, flashing of the full lamp 440 may be extinguishedby' turningthe manual mode selector switch to the PACK- RETURN position which causes theoff terminal 148 to drop in voltage.
Directing attention now to thereturn function, this function is useful for returning thepressure plate 30 to its uppermost position after the baling operation or after, any machine malfunction or other occurrence leaves the pressure plate 30 in any position except its uppermost position. One example of an occurrence which leaves the pressure plate 30in a lowered position is the opening of either compactionchamber door 16, 28 while the pressure plate 30 is in motion. This causes '17 the magnetically actuated switch 130 to open whereupon movement of the pressure plate 30 immediately ceases.
-It will be recalled that whenever the pressure plate 30 is not in its uppermost position, the low limit switch 164 472 which is referenced to ground, a pair of voltage reference resistors 468, 470 and the directional diode "466. The gate terminal of the PUT 474 is connected to a resistor 476 which is referenced to the dc. supply voltage at the capacitor 464. The cathode terminal of I the PUT 474 is connected to the gate biasing resistors 478, 480 of the return memory SCR 482. An additional .SCR 482 gate to cathode terminal bias resistor 484 is used. The anode terminalof the SCR'482 is connected .tothe hold terminal 170 throughthe line smoothing capacitor 492 and the directional diode454. The cathode terminal of the SCR 482 is referenced to ground through-the resistor 486and is connected-to the base terminal of the return current driving transistor 409 of the NPN type through the resistor 488. The emitter ter.-
minal of the transistor 490 is connected to ground while its collector terminal is connectedto the anode terminal of the bale memorySCR 266 andthe anode terminal of the drivedown memory SCR 242. The return logic generation transistor 462 of the NPN type has its base terminal connected to the pack initiate ter- I minal 152 through the directional diode 452 and the resistor 456 and is referenced totground through the resistor 458. Theemitter terminal of the transistor 462 is connected to ground while its collector terminal is 18 I supported by the capacitor'472, is at a higher potential than the gate terminal. The PUT 474 is triggered into conduction and thecapacitor 472 iis discharged through the cathode terminal of the PUT 474 and the resistor478. j j p The discharging through the resistor 478 generates a positive pulse to the gate terminal of the return memory SCR 482 through the gatebias'resistors480, 484. Since the anode terminal of the return memory SCR 482 is connected to the dc. supply voltage on the hold terminal 170 through the directional diode 454-, the
SCR 482 is triggered into conduction when the positive pulse is applied toits gate terminal. The conduction of SCR 482 drives the return driving transistor'490 into conduction by supplying base terminal current through the bias resistor 488. The conduction of transistor 490 'pulls the pressure plate drive down line, which is connected to the anode terminals of the bale memory SCR 266 and the drive down memory SCRJ242, down to ground potential. The SCR 266 and the SCR 242 are ,now deprived of anode voltage and any prior conductionceasesrThus, the return logic circuit450 cancels any prior bale'memory 180 and cancels any prior drive down memory 240. Thedirectional valve solenoid 72 is deenergized when the drive down memory 240 is cancelled and the directional valve 74 returns to is normal position. Note that when the return logic-circuit 450 was actuatedb'y a pulse on the pack initiate terminal Y152 and the d.c.', supply voltage on the holdterminal the hold terminal 170 on its anode terminal. and the connected to the capacitor 464 and the resistors460,
The return circuit 450 functions to deenergize the bale memory circuit 180 and the 'drive down memory circuit 240 inth anner hereinafter described. The return circuit 450 receives d.c. supply voltage from the hold'terminal 170 through the directional diode 454. The capacitor'464 rapidly charges toward the dc. supply voltage through the resistor 460. The capacitor 472 charges rapidly toward the voltage reference level determined by the voltage reference resistors 468, 470. When the operator wishes to return the pressure plate 30 toward its uppermost position, the manual mode selector switch 140 is turned to the PACK-RETURN position. A pack initiate pulse is then generated at the pack initiate terminal .152 which is conducted to the base of the return logic transistor462through the R-C decoupling network 188, the directionaldiode 452 and the resistor 456. Thepack initiate signal at the base terminal of the transistor, 462 causes the transistor 462 to conduct; thecollector terminal dropping in voltage to nearly ground potential. The capacitor 464 israpidly discharged through the transistor 462 and the gate terminal of the return pulse generator PUT 474 is pulled toward ground potential through the resistor 476. The
anode terminal of the PUT 474 momentarilystays at anode terminal of the PUT 474, which has its potential pack initiate pulse'from the pack initiate terminal 152 on its gate terminal. Thus, the motor drive relay 172. is
energized by the packrnemory SCR 184 supplying d.c.' voltage to the motor relay driver circuit186. With the hydraulic solenoid74 in its normal position and the hydraulic motor 68 running, the pressure plate 30 retracts toward its uppermost position. When the pressure plate 30 reaches its uppermost position, or when refuse is lodged between the compaction chamber topplate l1 and the pressure plate 30, the high limitswit'ch 164 assumes itsnormally open position'causing the dc. sup.-
ply voltage on the hold terminal l'70'to drop. When refuse is solodged in the space abovethe pressure plate 30, the plate 30' upon stopping does not return to'its-uppermost position, but resumes its next downward stroke from this starting position. Since bias and drive current for the return logic circuit 450 is supplied by the hold terminal 170, the return pulse generator PUT 474, the return memory SCR'482 and the return driver transistor 490 are disabled. The directional diode 466 now allowsrapid discharge of thecapacitor472 to prevent further PACK-RETURN cominandsfrom the operator from generating another return signal.
It will be understood from the above circuitdescription that if the capacitor 472 was not fully discharged, another return pulse would be generated by the Put 474 whenever the manual mode selector switch is turned to the PACK-RETURN or BALE positions thereby supplying voltage to the hold terminal through the directional diodes 198, 292. This would resultin the undesirable system operation of inhibiting any downward movement of the pressure plate 30. The
directionaldiode 466 provides a rapid discharge path for the capacitor472 and eliminates this problem. If the capacitor 472 is discharged, no such hazard occurs when the manual mode selector switch 140 initiates the PACK-RETURN or BALE functions as described above.
Turning now to the automatic shut-off function, this function deenergizes the drive motor after a predetermined short period of time, eg 45 seconds, beyond the initiation of any operation by the operator. This function prevents damage to the unit or injury to the opera-.
tor which might result from any system malfunction.
The automatic shut-off function is performed by'the end cycle timer circuit 500. The dc. supply voltage for the end timer circ'uit 500 is derived directly from the pressure plate drive down terminal 166. The end cycle PUT 502 has its gate terminal connected to a pair of voltage reference resistors 508, 510 and its anode terminal connected to a timing resistor 504-referenced to the dc. supply voltage and a timing capacitor 506 referenced to ground. The timing capacitor 506 charges through the timing resistor 504 until the anode terminal potential of the PUT 502 reaches the potential of the gate terminal. The PUT 502 is then triggered into conduction and the timing capacitor 506 is discharged through the PUT 502 cathode terminal and the resistor 512 which is referenced to ground. The delay time of the pulse which is generated at the resistor 512 is directly proportional to the selected values of the timing resistor 504 and the timing capacitor 506, the values being selected toproduce a short' delay time, e.g. of about.45 seconds. The delay pulse generated at the resistor 512 drives a pair of transistors 514 and 516 of the NPN type and connected in the Darlington configuration. The base terminal of the transistor 514 is connected to the discharge resistor 5112 and the PUT 502 cathode terminal and'the emitter terminal of the transistor 514 is connected to the base terminal of the transistor 516. The transistor 516 has its emitter connected to ground. The collectors of both transistors 514, 516 are connected directly to the pressure plate drive down terminal 166. v
' When the pressureplate 30 leaves its uppermost po- 20 H malfunctionis repaired, the pressure plate can be retracted to its uppermost position by using the previously described return function.
If the pressure plate 30 reaches maximum compression pressure within the exemplary 45 second delay of the end cycle timer circuit 500, the circuit 500- is reset to begin another 45 second delay period when the pressure plate 30 beginsretracting toward its uppermost position. The interruption of the dc. supply voltage on the pressureplate drive down terminal 166 by the compression pressure switch 160 causes the gate terminal of the PUT 502 to drop in voltage along with the pressure plate drive down terminal. However, the voltage of the anode terminal of the PUT 502 is-supported by the timing capacitor 506. As the voltage of the gate terminal of the PUT 502 drops below that of the anode terminal, the PUT 502 is triggered into conduction and the timing capacitor 506 .is discharged through the cathode terminal of the PUT 502, the discharge resistor 512 and the drive down transistors 514, 516. Thus,.the end cycle timer circuit 500 is reset to begin another delay period to deenergize the motor drive relay in the event that some malfunction prevents the pressure plate 30 from reaching its uppermost position within45 seconds.
7 Note that the pressure plate 30 retraction is automatic when the system is in the compaction mode and must be manually. initiated by themanual modeselector switch 140 when the system is in the bale mode. However, the delay period does not begin until the system is manually initiated (assuming no leakage of hydraulic fluid and consequent loss of fluid pressure due to-leaky seals and the like) when it is in the bale mode because of the opening of the'compression pressure switch 160 when maximum compression pressure is achieved deprives the endcycle timer circuit500 of do. supply .voltage.
Similarly, when the system'is in the tamp mode, each achievement of maximum compress'ionpressure of the pressure plate 30 opens the pressure switch 160 and interrupts the dc. supply voltage to theend cycle timer circuit 500. The circuit 500 is thereby reset to begin ansition, the high limit switch 172 closes and dc. supply within seconds, in this example, thereby opening the compression pressure switch 160, the PUT 502 is triggered into conduction as previously described. The
-,delay pulse from the PUT 502 cathode terminal drives the end cycle driver transistors 514, 516 into conduction which causes the dc. supply voltage on the pressure plate drive down terminal 166 to drop. Since the hold terminal 170 is connected to the pressure plate drive down terminal 166 through the compression pressure switch 160, the dc. voltage level of the hold terminal 170 drops with that of the pressure plate drive down terminal 166. The drop in voltage on both of these terminals causes the anode terminals of the pack memory SCR 184 and the bale memory SCR 266 to cease any prior conduction. Since the motor relay driver circuit 186, which energizes the motor relay 72, receives its d.c. supplyvoltage-from either of the SCRs 184, 266, the motor relay circuit 186 and the motor relay 72 are deenergized. Thus, the drive motor 68 is deactivated and the pressure plate 30 ceases any motion. After the other delay period for each change in directionlof the pressure plate 30. The end cycle timer circuit 500 has no effect .on norrna'lcompaction cycles sincenormal movementof the pressure plate.30 in any direction ceases ,within the delay period.
The above discussion has described the five principal functions of the system:' the compact function, the bale function, the tamp function, the return function and the automatic shut-off function. The accessory relay driver circuit 520 illustrates the capability of adding additional control functions to the system. This circuit 520 is presented forillustrative purposes only and to indicate the versatility of the control system in allowing additional user-desired functions to be implemented.
Such user-desired functions may include,'.but are not limited to, automatic cycling devices to initiate compaction cycles at predetermined time intervals.
I claim as my invention:
1. A control system for a'compacting machine having a compaction chamber for receiving material to be compacted, a pressure plate spanning the area of said chamber for compressing the contents thereof, a reversible drivesource for moving said pressure plate in the forward and reverse directions within said compaction chamber, sensing means associated with saiddrive to retract the pressure plate and permit removal of the compressed contents from the compaction chamber,
said control system-including means for initiating the forward operation of said drive source, emergency shut-off means including a) time delay means responsive to the initiation of said forward operation for producing an output at a predetermined interval after said initiation of forward operation, and b) means responsive to said output for inhibiting further operation of said drive source, saidtime delay interval being sufficiently long to enable normal forward or reverse operation of .said pressure plate to be completed before said tion thereof by rendering said drive source inoperative wheneverthe pressure plate reaches said fully retracted position, and said sensing means also being responsive output is produced and sufficiently long to enable normal forward or reverse operation of said pressure plate to be completed before said outp0ut is produced and sufficiently short to allow said output to be produced as soon as the period of operation of said drive source exceeds thetime normally required for full forward or reverse travel of said pressure plate.
'2..A control system for a compacting machine having a compaction chamber for receiving material to be compacted, a pressure platespanning the area of said chamber for compressing the contents thereof, a reversible drive source for moving said pressure plate in the forward and reverse directions within said compaction chamber, and a panel at the top of the compaction chamber for enclosing said chamber, said control system including means for sensingthe fully retracted position of said pressure plate to prevent'fu'rther retracto, theposition of the compaction chamber panel to render said drive source inoperative whenever material lodged between the pressure plate and the compaction chamber panel causes said panel to flex as the pressure plate retracts thereby preventing damage to said compaction chamber panel 'by the retracting pressure plate.
3. A control system according to claim 2 wherein the retraction position sensing means comprise a slidably mounted rod projecting'through thecompaction-chamber panel, said rod being engageable by the retracted pressure plate to slidably move upwardly and. thereby render said drive inoperative. I a
4. A control system for acompacting machine having a compaction chamber for receiving material to be compacted, a'pressure plate spanning the area of said chamber for compressing the contents thereof, a reversible drive source for moving said pressure plate in the forward and reverse directions within said compaction chamber, a panel at the top of the compaction chamber for enclosing said chamber, retraction position sensing meanscomprising a slidably mounted rod projecting through the compaction chamber panel, said rod being engageable by theretracted pressure plate to slidably move upwardlyand thereby render said drive inoperative, said retraction position sensing means further including a second retraction position sensing means mounted on saidrod and in engagement with the compaction chamber panel so that material lodged between the top of said pressure plate and said panel causes said panel to flex upwardly during retraction of saidpressure plate thereby causing upward movement of both the second retraction position sensing means and the rod to render the drivesource inoperative and thereby inhibit further retraction of said pressure plate.