Conveyor

Information

  • Patent Grant
  • 6497320
  • Patent Number
    6,497,320
  • Date Filed
    Wednesday, February 28, 2001
    23 years ago
  • Date Issued
    Tuesday, December 24, 2002
    21 years ago
Abstract
A conveyor has a rotary encoder for measuring the amount of rotation of a driven sprocket having an intermittently drivable chain reeved therearound, and a processor for processing the measurement obtained by the encoder as operation support operating data corresponding to the amount of rotation of the driven sprocket. The processor determines a reference position of the chain in time series when the chain is moved a distance at a time by intermitting driving, computes the actual position of the chain corresponding to the reference position based on the measurement obtained by the encoder, and computes the deviation of the actual position of the chain from the reference position.
Description




BACKGROUND OF THE INVENTION




The present invention relates to container conveyors, for example, for use in packaging machines.




Conveyors of the type mentioned are already known which comprise a drive sprocket, a driven sprocket, a chain reeved around the sprockets and drivable intermittently, and a plurality of container holders attached to the chain at a spacing corresponding to the distance the chain is moved at a time by intermittent driving. The chain has a container transport path extending successively via a group of devices including a filling device and a sealing device.




With the conveyor described, the container holders need to be brought to a halt accurately at specified operating positions such as the locations of the filling device and the sealing device. Otherwise, the required packaging operation will not be performed on the containers. However, the chain becomes inevitably stretched with time, and if exceeding a certain limit, the stretch starts to cause trouble in the packaging operation. Although maintenance is provided on the conveyor in the event of trouble arising, the procedure performed is not efficient.




SUMMARY OF THE INVENTION




An object of the present invention is to provide a conveyor wherein operation support operating data, for example, as to the halted position and movement of the chain is readily available to ensure facilitated and efficient maintenance of the chain.




The present invention provides a conveyor comprising a drive sprocket, a driven sprocket and an intermittently drivable chain reeved around the sprockets, the conveyor being characterized in that the conveyor comprises an instrument for measuring the amount of rotation of the driven sprocket, and a processor for processing the measurement obtained by the instrument as operation support operating data corresponding to the amount of rotation of the driven sprocket.




With the conveyor of the invention, the amount of rotation of the driven sprocket is measured to obtain operation support operating data based on the measurement. This assures the chain of facilitated and efficient maintenance.




The processor comprises setting means for determining a reference position of the chain in time series when the chain is moved a distance at a time by intermitting driving, means for computing the actual position of the chain corresponding to the reference position based on the measurement obtained by the instrument, and means for computing the deviation of the actual position of the chain from the reference position. This enables the operator to observe the dynamic variations involved in the movement of the chain when it is moved a specified distance at a time by intermittent driving.




The processor may comprise setting means for determining a reference halted position of the chain every time the chain is moved a distance by intermitting driving during one turn of movement, means for computing the actual halted position of the chain corresponding to the reference halted position based on the measurement obtained by the instrument, and means for computing the deviation of the actual halted position of the chain from the reference halted position. This enables the operator to observe the static variations involved in one turn of movement of the chain.




The present invention provides another conveyor comprising a pair of drive sprockets, a pair of driven sprockets and a pair of intermittently drivable chains each reeved around the drive sprocket and the driven sprocket corresponding to the chain, the conveyor being characterized in that the conveyor comprises a first instrument for measuring the amount of rotation of one of the driven sprockets, a second instrument for measuring the amount of rotation of the other driven sprocket, and a processor for processing the measurements obtained by the two instruments as operation support operating data.




The invention is useful also for the maintenance of the pair of chains included in this conveyor.




The processor of the conveyor comprises setting means for determining reference halted positions of the respective chains every time the chains are moved a distance by intermitting driving during one turn of movement, means for computing the actual halted position of each of the chains corresponding to the reference halted position of the chain based on the measurement obtained by the corresponding instrument, and means for computing the deviation of the actual halted position from the reference halted position. This enables the operator to observe the static variations involved in one turn of movement of the pair of chains.




When a plurality of container holders are attached to the chain at a spacing corresponding to the distance the chain is moved at a time by intermittent driving, and further when the chain has a container transport path extending successively via a group of devices including a filling device and a sealing device, each container holder can be brought to a halt at a desired operating position of the group of devices.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is an overall side elevation showing a packaging machine including a conveyor embodying the invention;





FIG. 2

is a perspective view of the conveyor of the invention;





FIG. 3

is a diagram showing the construction of a data processor for the conveyor;





FIG. 4

is a graph showing the operation waveform of driven sprockets;





FIG. 5

is a graph showing part of

FIG. 4

on an enlarged scale;





FIG. 6

is a graph showing variations in the amount of movement of a left driven sprocket; and





FIG. 7

is a graph showing variations in the amount of movement of a right driven sprocket.











DESCRIPTION OF THE PREFERRED EMBODIMENT




An embodiment of the present invention will be described below with reference to the drawings.




As shown schematically in its entirety in

FIG. 1

, a packaging machine comprises a container bottom forming rotor


12


provided with radial mandrels


11


each having fitted therearound a container C of square to rectangular cross section and intermittently drivable counterclockwise, and a container conveyor


13


having a transport path forwardly extending from below the rotor


12


.




Arranged one after another around the rotor


12


toward the direction of rotation of the rotor are a feeder


21


, bottom heater


22


, bottom breaker


23


, folding rail


24


, bottom press


25


and unloader


26


. Successively arranged along the path of transport of the conveyor


13


are a primary top breaker


31


, filling device


32


, secondary top breaker


33


, top heater


34


and top sealing device


35


.




With reference to

FIG. 2

, the conveyor


13


comprises a pair of left and right vertical drive shafts


41


A,


41


B, a pair of left and right vertical support rods


42


A,


42


B arranged in the rear of and spaced apart from these drive shafts


41


A,


41


B, upper and lower two left drive sprockets


43


A fixed to the left drive shaft


41


A and vertically spaced apart, upper and lower two right drive sprockets


43


B fixed to the right drive shaft


41


B and vertically spaced apart, upper and lower two left driven sprockets


44


A mounted on the left support rod


42


A and vertically spaced apart, upper and lower two right driven sprockets


44


B mounted on the right support rod


42


B and vertically spaced apart, upper and lower two left chains


45


A reeved around the left drive sprockets


43


A and the left driven sprockets


44


A at upper and lower levels, respectively, upper and lower two right chains


45


B reeved around the right drive sprockets


43


B and the right driven sprockets


44


B at upper and lower levels, respectively, and a horizontal guide rail


46


extending forward below the space between the left and right chains


45


A,


45


B.




A pair of left and right rotary encoders


49


A,


49


B are connected to the respective drive shafts


41


A,


41


B. Among the two left and two right driven sprockets


44


A,


44


B at the upper and lower levels, the left and right driven sprockets


44


A,


44


B at the upper level have a pair of left and right rotary encoders


55


A,


55


B, respectively.




The support rods


42


A,


42


B are supported upright on free ends of a pair of left and right horizontal pivotal arms


52


A,


52


B, respectively. A pair of fluid pressure cylinders


53


A,


53


B are directed rearward and have piston rods, which are connected to the respective support rods


42


A,


42


B. The fluid pressure cylinders


53


A,


53


B are horizontally pivotably supported at their cylinder side, and the piston rods can releasably be locked at a desired advanced or retracted position by the respective lock mechanisms


54


A,


54


B. The cylinders


53


A,


53


B each have incorporated therein a distance (displacement) sensor for measuring the amount of advance or retraction of the piston rod.




A plurality of L-shaped vertical pieces


56


A extend between and are attached to the two left chains


45


A, and a plurality of L-shaped vertical pieces


56


B corresponding to the pieces


56


A extend between and are attached to the two right chains


45


B.




With reference to

FIG. 2

, a servomotor


51


intermittently drives the left drive shaft


41


A counterclockwise when seen from above, and the right drive shaft


41


B clockwise as timed with the shaft


41


A, whereby the opposed portions of the left and right chains


45


A,


45


B are moved forward, providing a path of movement for feeding. Each pair of L-shaped pieces


56


A and each pair of L-shaped pieces


56


B on the respective left and right chains


45


A,


45


B form a holder. The holder traveling the feeding path fits to the four corners of the container C, which is transported with its bottom supported by the guide rail


46


.




The servomotor


51


is controlled by an unillustrated controller, and the chains


45


A,


45


B can be brought to a halt at desired positions, for example, with pulses provided by the controller.




When the chains


45


A,


45


B become stretched owing to the operation of the conveyor over a prolonged period of time, the piston rods of the fluid pressure cylinders


53


A,


53


B are advanced as unlocked from the lock mechanisms


54


A,


54


B, causing the cylinders


53


A,


53


B to apply pressures to the chains


45


A,


45


B to make the chains


45


A,


45


B taut. The piston rods are then locked by the lock mechanisms


54


A,


54


B again. This procedure is advantageous from the viewpoint of the stretch of the chains


45


A,


45


B since the pressures of the cylinders


53


A,


53


B will not act on the chains


45


A,


45


B at all times. However, the chains


45


A,


45


B may be subjected to the pressures at all times as the case may be. The chains


45


A,


45


B are then used always as tensioned.




The pressures to be applied to the chains


45


A,


45


B by the fluid pressure cylinders


53


A,


53


B respectively may be the same in magnitude, or one pressure may be made greater than the other in accordance with the difference between the two chains


45


A,


45


B in stretch.




The angles of rotation of the left and right drive sprockets


43


A,


43


B are measured individually by the drive-side rotary encoders


49


A,


49


B, while the angles of rotation of the left and right driven sprockets


44


A,


44


B are measured individually by the driven-side rotary encoders


55


A,


55


B.




Procedures will be described below for effectively utilizing the values measured by the drive-side and driven-side rotary encoders


49


A,


49


B,


55


A,


55


B, by processing the measurements as operation support operating data.





FIG. 3

is a diagram showing the construction of a processor


61


for a system for maintaining and supporting the operation of the conveyor. The processor


61


has a computing unit


62


, which receives the measurements from the drive-side and driven-side rotary encoders


49


A,


49


B,


55


A,


55


B. The unit


62


performs the required computation based on the measurements, and the result of computation is sent to a recorder


64


via a D/A conversion unit


63


and also to a display


65


. The recorder


64


records the result of computation, while the display


65


shows the result. If the result of computation is abnormal on the other hand, the computation unit


62


delivers a stop signal and an alarm signal. The conveyor is brought out of operation in response to the stop signal, while an alarm


66


gives a warning.




The drive-side rotary encoders


49


A,


49


B are driven by the servomotor


51


, therefore operate ideally at all times and can accordingly be dispensed with. These encoders


49


A,


49


B are used in the present embodiment in view of the mechanical loss involved in the path from the servomotor


51


to the drive shafts


41


A,


41


B, and the pulse signals produced by the encoders


49


A,


49


B are used for providing reference values. The driven-side rotary encoders


55


A,


55


B produce pulse signals corresponding to the actual angles of rotation of the driven sprockets


44


A,


44


B and to be used as actual values. The pulse signals are converted into the angles of the rotation of the drive and driven sprockets


43


A,


43


B,


44


A,


44


B in proportion thereto and into the amounts of movements of the chains (as reeved around the sprockets) in proportion to the signals.





FIG. 4

shows operation waveforms of the drive and driven sprockets


43


A,


43


B,


44


A,


44


B every time the conveyor is moved a distance by being driven intermittently (each conveyor cycle). Plotted as abscissa is time vs. the angle (dimensionless) of rotation of the drive and driven sprockets as ordinate. Each wave of the operation waveform indicated at A represents the operations of the drive and driven sprockets


43


A,


43


B,


44


A,


44


B corresponding to one conveyor cycle. The waveform A is reset every cycle and returns to the origin. Since there is no difference that is discernible in the waveform A between the operations of the drive and driven sprockets


43


A,


43


B,


44


A,


44


B, the operations appear to be represented by a single common line. Accordingly, the difference in operation waveform between the drive and driven sprockets


43


A,


43


B,


44


A,


44


B is represented as enlarged 20 times by a waveform B.





FIG. 5

shows one cycle of the operation waveform of

FIG. 4

as enlarged with respect to time. It is seen that the operation of the driven sprockets


44


A,


44


B lags behind the operation of the drive sprockets


43


A,


43


B by a maximum deviation G immediately after the start of travel of the chains, thereafter gradually recovers and overtakes the operation of the drive sprockets


43


A,


43


B immediately before halting and comes to a halt after going on ahead of the operation of the drive sprockets.

FIGS. 4 and 5

indicate dynamic variations in the operation of the chains during one cycle of conveyor operation.




The lag of the operation of the driven sprockets


44


A,


44


B, namely, the deviation G of the operation of the driven sprockets


44


A,


44


B from the operation of the drive sprockets


43


A,


43


B, indicates the degree to which the driven sprockets


44


A,


44


B follow the drive sprockets


43


A,


43


B and which corresponds mainly to the slackening of the chains


45


A,


45


B due to a stretch. The greater the deviation, the greater the tendency for the chains


45


A,


45


B to operate abruptly inadvertently, consequently greatly rocking the liquid filled in the container C as held by the holder. If the liquid is rocked to spill, a faulty seal will result. If the deviation exceeds a predetermined value, the computing unit


62


outputs a stop signal and an alarm signal, and required maintenance is provided. The predetermined value of deviation is, for example, 7 degrees.




Local faults in the chains


45


A,


45


B, biting of containers, application of an abnormal load or like trouble can be detected by monitoring the waveforms shown in

FIGS. 4 and 5

at all times to halt the conveyor in an emergency.





FIGS. 6 and 7

show variations in the deviation of halted positions of the drive and driven sprockets


43


A,


43


B,


44


A,


44


B during each cycle of conveyor operation while the chains


45


A,


45


B make one turn,

FIG. 6

showing the data for the left chain


45


A, and

FIG. 7

the data for the right chain


45


B.




The period T


1


, T


2


for one turn of the chains


45


A,


45


B is plotted as abscissa, and successively plotted as ordinate is the variation in the halted position on completion of each cycle of conveyor operation during the period T


1


, T


2


. The origin


0


is always taken as the halted positions of the drive sprockets


43


A,


43


B, providing reference halted positions for the chains every time the chains are moved a specified distance by intermittent driving during one turn of movement of the chains. The waveforms CA and CB represent the actual deviations of the driven sprockets


44


A,


44


B from the origin


0


, in terms of variations in the halted position as converted in mm from the angle of rotation of each driven sprocket


44


A or


44


B. The waveforms CA and CB represent the data in the initial state, and the waveforms DA and DB represent the data available a specified period of time thereafter.




Noteworthy is the following fact. The pattern representing the variations in the deviation during each period T


1


or T


2


for one turn of movement of the chain has regularity, and the same pattern is available in each period T


1


or T


2


.




The chains


45


A,


45


B stretch with time, and the resulting variations are manifest in the transition from the waveforms CA and CB to waveforms DA and DB, and are static variations. The time taken for the deviation in the pattern reaches a limit necessitating maintenance can be estimated by measuring the static variations with the lapse of time. Based on the estimated result, the computing unit


62


produces a stop signal and alarm signal. The limit of deviation is, for example, 2.0 mm at the location of the driven sprockets


44


A,


44


B, 2.0 mm at the location of the filling device, or 1.5 mm at the location of the sealing device.




If the pattern deviates toward the positive direction to reach the limit, adjustment is so made as to halt the chain


45


A or


45


B at a position shifted toward the negative direction. Containers C can then be halted at a desired operating position such as the location of the filling device, sealing device, or the like.




In the case where the pattern deviates toward the positive direction as the chain


45


A or


45


B stretches as described above, it is possible to lengthen the time taken for the deviation of the pattern to reach a limit necessitating maintenance, by causing the chain


45


A or


45


B to halt, for example, at a specific position in the pattern where the variation of the halted position is minimum, and adjusting the halted position of the chain


45


A or


45


B so that this position is close to the limit value at the negative side. Conversely, in the case where the pattern deviates toward the negative direction as the chain


45


A or


45


B stretches as described above, it is possible to lengthen the time taken for the deviation of the pattern to reach a limit necessitating maintenance, by causing the chain


45


A or


45


B to halt, for example, at a specific position in the pattern where the variation of the halted position is maximum, and adjusting the halted position of the chain


45


A or


45


B so that this position is close to the limit value at the positive side.




Although the embodiment described is adapted to measure the angles of rotation of the left and right drive and driven sprockets, the present invention can be practiced merely by measuring the angle of rotation of at least one driven sprocket. Furthermore, other device such as a laser sensor is usable in place of the rotary encoder for measuring the angle of rotation of the driven sprocket.




When the measuring instrument is provided for each of the left and right driven sprockets, the deviation patterns of the respective left and right chains are available. The deviation, in the transport direction, of the container holders (vertical L-shaped pieces) provided on the respective chains can be diminished by making such adjustment as to ensure synchronism between the two patterns.




The left and right drive sprockets may be driven by a single servomotor, whereas if these sprockets are driven individually by separate servomotors, the above adjustment can be effected automatically.




The driven sprockets and the vicinity thereof (the portion where containers are fed to the conveyor in the case of the present embodiment) which are liable to malfunction due to a stretch of the chain can be reliably monitored by providing the instrument for measuring the amount of rotation of the driven sprocket, whereby the trouble is avoidable.




The upstream side of the conveyor with respect to the container transport direction may serve as the drive portion, with the downstream side serving as the driven portion.



Claims
  • 1. A conveyor comprising a drive sprocket, a driven sprocket and an intermittently drivable chain reeved around the sprockets, the conveyor being characterized in that the conveyor comprises an instrument for measuring the amount of rotation of the driven sprocket, and a processor for processing the measurement obtained by the instrument as operation support operating data corresponding to the amount of rotation of the driven sprocket, wherein the processor comprises:setting means for determining a reference halted position of the chain every time the chain is moved a distance by intermitting driving during one turn of movement, means for computing the actual halted position of the chain corresponding to the reference halted position based on the measurement obtained by the instrument, and means for computing the deviation of the actual halted position of the chain from the reference halted position.
  • 2. A conveyor according to claim 1 wherein the processor comprises setting means for determining a reference position of the chain in time series when the chain is moved a distance at a time by intermitting driving, means for computing the actual position of the chain corresponding to the reference position based on the measurement obtained by the instrument, and means for computing the deviation of the actual position of the chain from the reference position.
  • 3. A conveyor comprising a pair of drive sprockets, a pair of driven sprockets and a pair of intermittently drivable chains each reeved around the drive sprocket and the driven sprocket corresponding to the chain, the conveyor being characterized in that the conveyor comprises a first instrument for measuring the amount of rotation of one of the driven sprockets, a second instrument for measuring the amount of rotation of the other driven sprocket, and a processor for processing the measurements obtained by the two instruments as operation support operating data, wherein the processor comprises:setting means for determining a reference halted positions of the respective chains every time the chains are moved a distance by intermitting driving during one turn of movement, means for computing the actual halted position of each of the chains corresponding to the reference halted position based on the measurement obtained by the instrument, and means for computing the deviation of the actual halted position of the chain from the reference halted position.
  • 4. A conveyor according to any of claims 1, 2 and 3 wherein a plurality of container holders are attached to the chain at a spacing corresponding to the distance the chain is moved at a time by intermittent driving.
Priority Claims (1)
Number Date Country Kind
2000-055219 Mar 2000 JP
US Referenced Citations (5)
Number Name Date Kind
2794536 Roza et al. Jun 1957 A
4172347 Nitz Oct 1979 A
4641742 Igarashi et al. Feb 1987 A
4818540 Chien et al. Apr 1989 A
5337885 Mills et al. Aug 1994 A
Foreign Referenced Citations (3)
Number Date Country
0 574 087 Dec 1993 EP
0 945 372 Mar 1999 EP
WO 9641760 Dec 1996 WO