Abstract:
An individual section (IS) machine glassware forming system includes an individual section machine with a plurality of individual sections for receiving gobs of molten glass and forming the gobs into articles of glassware. A gob feeder presents gobs of molten glass, and a gob distributor feeds the gobs to the individual machine sections in sequence. Operation of the machine sections is synchronized to operation of the glass feeder by generating a feeder index signal indicative of presentation of glass gobs at the glass feeder. An electronic machine timing circuit includes facility for electronically generating a machine index signal for synchronizing operation of the machine sections with respect to each other. Separation in real time between the feeder index signal and the machine index signal during system operation is determined and stored in units of time. Upon initialization of operation of the system after shutdown for any reason, this stored time is automatically retrieved, and timing of the machine index signal is automatically adjusted relative to the feeder index signal to equal this stored time.

Description:
The present invention is directed to individual section (IS) machine glassware forming systems, and more particularly to a method and apparatus for synchronizing the timing of machine operation to the provision of molten glass gobs to the IS machine. 
     BACKGROUND AND OBJECTS OF THE INVENTION 
     The art of glass container manufacture is currently dominated by the so-called individual section or IS machine. Such machines include a plurality of separate or individual manufacturing sections, each of which has a multiplicity of operating mechanisms for converting one or more charges or gobs of molten glass into hollow glass containers and transferring the containers through successive stages of the machine section. In general, an IS machine system includes a glass source with a needle mechanism for controlling a stream of molten glass, a sheer mechanism for cutting the molten glass stream into individual gobs, and a gob distributor for distributing the individual gobs among the individual machine sections. Each machine section includes one or more blank molds in which a glass gob is initially formed into a parison in a blowing or pressing operation, one or more invert arms for transferring the parisons to blow molds in which the containers are blown to final form, tongs for removing the formed containers onto a deadplate, and a sweepout mechanism for transferring molded containers from the deadplate onto a cross conveyor. The conveyor receives containers from all sections of an IS machine in sequence, and conveys the containers to a loader for transfer to an annealing lehr. Operating mechanisms in each section also provide for closure of mold halves, movement of baffles and blowing nozzles, control of cooling wind, etc. U.S. Pat. No. 4,362,544 includes a background discussion of the art of both “blow and blow” and “press and blow” glassware forming processes, and also discusses an electropneumatic individual section machine adapted for use in either process. 
     A critical requirement in glassware forming systems of this character, both during initialization and during continuing operation, is to synchronize operation of the glassware forming machine to the sequential supply of molten glass gobs. Operation of the various machine sections is electronically synchronized by a machine reset signal. A signal may also be provided by the gob feeder mechanism, generated either by a sensor or electronically responsive to feeder control electronics. It is proposed in Canadian Patent 1,198,793 to provide a counter responsive to clock signals from the various operating mechanisms, such as the gob feeder and the machine reset signal, for measuring offset therebetween in units of machine degrees. These offsets are manually noted, and manually reset upon the initialization after shutdown. However, gob travel time from the feeder to the blank molds is relatively constant in real time, and does not vary with machine speed. Thus, setting offset times in units of machine degrees does not provide adequate synchronization as machine speed varies. Furthermore, timing adjustments are made manually rather than automatically in the noted patent. 
     U.S. Pat. No. 4,108,623 discloses an IS machine control system that operates in real time, as distinguished from operating in machine or section degrees as is more typical in the art. The time between gob shear and entry into the blank mold is measured by employing a first sensor for generating a signal indicative of entry of a gob into the gob distributor, and a second sensor for generating a signal indicative of entry of the gob into the blank mold. Mold operation is initiated by the sensor responsive to gob entry into the mold. There is no fixed time between shear cut and operation of the blank mold. 
     It is a general object of the present invention to provide a method and system for synchronizing operation of the forming machine to provision of molten glass gobs in an IS machine glassware forming system that automatically synchronize operation upon initialization of the system, and that automatically maintain such synchronization during system operation. 
     SUMMARY OF THE INVENTION 
     An individual section (IS) machine glassware forming system includes an individual section machine with a plurality of individual machine sections for receiving gobs of molten glass and forming the gobs into articles of glassware. A gob feeder presents gobs of molten glass, and a gob distributor feeds the gobs to the individual machine sections in sequence. In accordance with the present invention, operation of the machine sections is synchronized to operation of the glass feeder by generating a feeder index signal indicative of presentation of glass gobs at the glass feeder. An electronic machine timing circuit includes facility for electronically generating a machine index signal for synchronizing operation of the machine sections with respect to each other. Separation in real time between the feeder index signal and the machine index signal during system operation is determined and stored in units of time. Upon initialization of operation of the system after shutdown for any reason, this stored time is automatically retrieved, and timing of the machine index signal is automatically adjusted relative to the feeder index signal to equal this stored time. 
     Thus, the time between the feeder index signal and the machine index signal is used for automatically restoring synchronization of the machine upon start-up or initialization. The feeder index signal is generated indicative of presentation or shearing of each molten glass gob, either by means of a sensor that is responsive to mechanical operation of the shear mechanism, or by monitoring operation of an electronic cam associated with the shear blades. A first of these shear signals is automatically arbitrarily associated with a first of the machine sections to provide a feeder index signal associated with presentation of a gob for the first machine section. An electronic synchronization controller automatically generates a machine index signal that, together with appropriate offsets generated for each section by section control electronics, synchronizes operation of the several machine sections to each other. The time between the feeder index signal generated by presentation of the gob for the first machine section, and the machine index signal that initiates operation of the first machine section, is measured during operation in units of time and stored in memory. Upon re-initialization of the IS machine, this time is retrieved from memory, and the machine electronic timing system is automatically adjusted until the time between the feeder index signal and the machine index signal is again equal to this stored time. This timing adjustment preferably is carried out by means of a phase-locked loop in incremental phase adjustments of a magnitude selectable by an operator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with additional objects, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which: 
     FIG. 1 is a functional block diagram of an individual section machine glassware forming system in accordance with which the present invention preferably is implemented; 
     FIG. 2 is a more detailed functional block diagram of a portion of the system illustrated in FIG. 1; 
     FIG. 3 is a functional block diagram of machine system timing and control electronics in accordance with a presently preferred embodiment of the invention; 
     FIG. 4A is a schematic diagram that illustrates various phases of molten gob travel from the gob shears to the blank molds in FIG. 2; 
     FIG. 4B is a graphic illustration of timing of the mechanisms of FIG. 4A; 
     FIG. 5 is a functional block diagram of a portion of the electronic controller in FIG. 3 for adjusting the phase relationship between the feeder index signal and the machine index signal in accordance with the present invention; and 
     FIGS. 6A and 6B together comprise a flow chart that illustrates operation of the phase adjustment in FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 illustrates an IS machine glassware forming system  10  as comprising a reservoir or bowl  12  containing molten glass (from a forehearth) that is fed by a needle mechanism  14  to a shear mechanism  16 . Shear mechanism  16  severs individual gobs of molten glass, which are fed by a gob distributor  18  to an IS machine  20 . IS machine  20  includes a plurality of individual sections  20   a,    20   b  . . .  20   n,  within which the gobs are formed into individual pieces of glassware. Each section terminates in a sweepout station, from which the articles of glassware are delivered to a common machine conveyor  22 . Conveyor  22 , usually an endless belt conveyor, delivers the containers in sequence to a lehr loader  24 , which loads the containers in batches into an annealing lehr  26 . The containers are delivered by lehr  26  to the so-called cold end  28  of the manufacturing cycle, at which the containers are inspected for commercial variations, sorted, labeled, packaged and/or stored for further processing. 
     System  10  illustrated in FIG. 1 includes a multiplicity of operating mechanisms for performing operations on the glass, moving glass workpieces through sequential stages of operation, and otherwise performing functions in the system. Such operating mechanisms include, for example, needle mechanism  14 , gob shear mechanism  16 , gob distributor  18  and lehr loader  24 . In addition, there are a multiplicity of operating mechanisms within each section of IS machine  20 , such as mechanisms for opening and closing the molds, mechanisms for in and out motions of the funnels, baffles and blow heads, mechanisms for motions of the invert arms and take-out tongs, and sweepout mechanisms for moving the ware onto machine conveyor  22 . 
     Referring to FIG. 2, each individual section  20   a,    20   b  . . .  20 , includes at least one and preferably a plurality of blank molds  30  that receive glass gobs simultaneously from gob distributor  18 . In the particular exemplary system illustrated in the drawings and herein discussed, machine  20  comprises a so-called triple-gob machine, in which each machine section includes three sets of blank molds  30  and three sets of blow molds  32  for operating simultaneously on three glass gobs to produce three pieces of glassware. So-called single, double and quad machines are also employed in the art. Glass gobs are delivered substantially simultaneously to the blank molds  30  of a given machine section, and are delivered to the blank molds of the several machine sections in the so-called firing order or sequence for which the system is designed. Glass gobs are simultaneously formed into parison blanks in molds  30 , and are simultaneously transferred by associated invert arms from blank molds  30  to blow molds  32 . At blow molds  32 , the parison blanks are blown to final form while the next series of parison blanks are formed in blank molds  30 . As the next series of parison blanks are transferred by the invert arms to blow molds  30 , the finished ware is transferred from blow molds  30  by takeout tongs to the deadplate of a sweepout station  34 . The several sweepout stations  34  are operated in sequence to deliver finished ware to machine conveyor  22  (FIG.  1 ). 
     To the extent thus far described, IS machine glassware forming system  10  is of conventional construction. Reservoir  12  and needle mechanism  14  may be as shown, for example, in U.S. Pat. No. 3,419,373. In a currently preferred embodiment of the invention, needle mechanism  14  is as disclosed in U.S. Pat. No. 5,693,114 and U.S. application Ser. No. 08/597,760. Gob shear mechanism  16  may be as in U.S. Pat. No. 5,573,570 or U.S. Pat. No. 5,772,718. Gob distributor  18  may be as in U.S. Pat. No. 5,683,485 or U.S. Pat. No. 5,697,995. U.S. Pat. Nos. 4,362,544 and 4,427,431 illustrate typical IS machines  20 , and U.S. Pat. Nos. 4,199,344, 4,222,480 and 5,160,015 illustrate typical sweepout stations. U.S. Pat. Nos. 4,193,784, 4,290,517, 4,793,465 and 4,923,363 illustrate suitable lehr loaders  24 . U.S. Pat. Nos. 4,141,711, 4,145,204, 4,145,205, 4,152,134, 4,338,116, 4,364,764, 4,459,146, 4,762,544, 5,264,473 and 5,580,366 illustrate various arrangements for electronic control of glassware manufacture in an IS machine system. A system for controlling motions of IS machine operating mechanisms is illustrated, for example, in above-noted U.S. Pat. No. 4,548,637. The disclosures of all U.S. patents and applications noted above, as well as the disclosure of Canadian Patent No. 1,198,793 noted above, are incorporated herein by reference for purposes of background. 
     A sensor  40  is functionally illustrated in FIG. 2 as being responsive to operation of gob shear mechanism  16  for generating an associated shear cut signal. Sensor  40  may comprise a proximity sensor or the like responsive to physical motion of the shear blades for generating the shear cut signal. Alternatively, in applications in which the shear blades are driven by an appropriate servo mechanism responsive to a stored electronic profile or cam, sensor  40  may comprise electronics that detect a predetermined position along the electronic cam profile for delivering the shear cut signal. The shear cut signal from sensor  40  is delivered to an electronic synchronization controller  42  in FIG.  3 . Controller  42  also receives an input frequency signal from a master oscillator. Controller  42  provides outputs to computerized section operator consoles or COMSOCs  44   a,    44   b,  . . .  44   n,  which control operation of associated machine sections  20   a,    20   b,  . . .  20   n,  respectively. COMSOC units  44   a - 44   n  may be as shown in U.S. Pat. Nos. 4,152,134, 4,364,764, 4,459,146, 5,264,473 and 5,580,306 for example. In the preferred implementation in which gob distributor  18  is electrically rather than mechanically driven, controller  42  also provides a control output to the gob distributor. Controller  42  also receives input from an operator keyboard  46 , and provides output to an operator display screen  48  for conventional display and control purposes. 
     FIG. 4A illustrates fall of a glass gob  50  from shears  16  through a scoop of gob distributor  18  to a blank mold  30  of an individual machine section. A gob  50  cut by shears  16  falls by gravity through suitable troughs to a scoop of gob distributor  18 , and thence by gravity either directly or through another trough to the blank mold  30  of an individual machine section. The scoop fall time SFT between shears  16  and scoop  18 , and the dwell time DT within scoop  18  remain relatively constant. Likewise, the total blank fall time BFT between shears  16  and a given blank mold  30  remains relatively constant, all in units of real time, although the blank fall time BFT for the differing machine sections may vary due to differing distances of physical separation between the machine sections and the gob distributor. The important point is that the scoop fall time SFT, scoop dwell time DT and the total blank fall time BFT for a given blank mold  30  all remain relatively constant in units of real time regardless of machine speed. Thus, referring to FIG. 4B, there is a relatively fixed total time SFT plus DT associated with each shear cut signal from sensor  40  (FIG.  1 ), independent of machine speed. Likewise, there is a relatively fixed time ST during which the scoops of the gob distributor may be moved for delivering gobs to the next section in sequence. Total blank fall time BFT is illustrated in FIG. 4B only for the first machine section. The shear cut signal associated with the first machine section is arbitrarily selected as the feeder index signal. (The “first” machine section need not necessarily be physically first in the IS machine, but is arbitrarily designated “first” in terms of the firing order of the machine.) 
     Turning to FIG. 5, each shear cut signal is fed in synchronization controller  42  to a gate  54 , which receives a second signal from a latch  56  that is set by the reference index signal. The reference index signal functions to select the shear cut signal associated with the first machine section as the feeder index output signal from gate  54 . A timer  58  is initiated or started by the feeder index signal, and receives the machine index signal as a second or stop input. Thus, the output of timer  58 , which indicates the offset or phase relationship between the feeder index signal and the machine index signal in units of real time, provides a control input to a phase adjustment control  60 . Phase adjustment control  60  also receives an input stored in memory  61  indicative of the desired phase relationship between the feeder and index signals, and an operator input (also stored in memory) indicative of the allowable rate of change of this phase relationship. The output of phase adjustment control  60  is fed to the divide-by-D module  62  of a phase-locked loop  64 . Phase locked loop  64  also has a divide-by-N module  66 , and receives an input frequency from an external control oscillator. Phase locked loop  64  in conjunction with modules  62 ,  66  may be as disclosed in U.S. Pat. Nos. 4,145,204 and 4,145,205, for example, the disclosures of which are incorporated herein by reference. The output of phase locked loop  64  at D module  62  provides the machine degree control signal (in units of time) to the remainder of the control electronics, and is fed through a divide-by-X module  68  to provide the machine index signal. Referring back to FIG. 4B, timer  58  measures the time between the feeder index signal and the machine index signal. The machine index signal, which synchronizes operation of all machine sections and initiates closure of the blank mold in the first section, occurs a time t prior to the end of the blank fall time BFT for section  1  to allow time for the blank molds to close prior to delivery of the glass gob. Phase locked loop  64  is also connected to a divide-by-D R  divider  67 , which is connected to a divide-by-X R  divider  69 . Dividers  67 ,  69  provide reference degree and reference index signals to the loader and feeder controls (not shown). Divider  69  also provides the set input to latch  56 . 
     In the preferred embodiment of the invention, controller  42  is implemented in a digitally-operated microprocessor-based controller. FIGS. 6A and 6B illustrate operation of timing controller  52 , including particularly operation of phase adjustment control  60 . Referring to FIG. 6A, the output of timer  58  (FIG. 5) is first obtained at  70 , and compared at  72  to the desired phase relationship between the feeder index and the machine index signals. This desired phase relationship is that stored in controller memory  61  when proper synchronization takes place, and is retrievable both on initialization and during operation of the machine. The difference in units of real time between the desired and actual phase is then compared at  74  to a dead band to prevent dithering. Blocks  76 ,  78 ,  80  and  82  determine whether it is necessary to adjust the phase relationship by increasing D (block  84 ) or decreasing D (block  86 ). Thus, if the value D at divider  92  is to be increased, this value is incremented at  84  by the allowable phase change increment D DELTA  set by the operator. Likewise, if the value D is to be decreased, this value is decremented at  86  by the allowable phase change increment D DELTA . An adjustment time T ADJ  is then computed at  88  and  90  as the product of T PHASE-DELTA  (block  72 ) times D NEW  divided by D DELTA . The divider factor D NEW  is then implemented at  92  for a time T ADJ , after which D OLD  is restored at  94 . Operation is then returned to FIG. 6A for comparing actual to desired phase, etc.