Abstract:
A machine ( 2 ) for handling partially formed containers ( 6 ) comprising an indexing conveying device ( 8 ), a feeder ( 4 ) arranged to supply to the conveying device ( 8 ), per index, a plurality of partially formed containers ( 6 ), one or more stations ( 18, 20 ) comprising a plurality of devices arranged to perform substantially identical operations on a group of containers constituted by the plurality of partially formed containers ( 6 ), the indexing conveying device ( 8 ) being arranged to advance the group through the stations ( 18, 20 ), and a controlling device arranged to cause the feeder ( 4 ) to reduce to an integer the number of partially formed containers ( 6 ) supplied, per index, to the conveying device ( 8 ). The machine ( 2 ) is operated by the controlling device via a number of servomechanisms associated with each of the operations carried out by the machine. One of the servomechanisms is used for homing a moving mechanical part ( 72 ) of the machine ( 2 ), a servo motor ( 84 ) driving the moving mechanical part ( 72 ), the controlling device controlling the servo motor ( 84 ), and a mechanical stop ( 76 ) for stopping the moving mechanical part ( 72 ) at a home position, wherein the controlling device is arranged to monitor servo motor power draw and to recognize the home position as corresponding to a position of the servo motor ( 84 ) when the servo motor power draw reaches a predetermined value.

Description:
This application is a National Stage of International Application No. PCT/GB2006/001590, filed May 2, 2006 which claims priority to U.S. Provisional Patent Application No. 60/676,886 filed May 2, 2005; U.S. Provisional Patent Application No. 60/676,903 filed May 2, 2005; U.S. Provisional Patent Application No. 06/676,915 filed May 2, 2005; U.S. Provisional Patent Application No. 06/676,916 filed May 2, 2005 and GB 0605136.1 filed Mar. 15, 2006. The disclosures of the above applications are incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     Not applicable. 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1 . Field of Invention 
     This invention relates to improvements in packaging apparatus and methods. 
     2 . Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
     Not applicable. 
     BRIEF SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, there is provided apparatus for handling partially formed containers comprising an indexing conveying device, a feeder arranged to supply to said conveying device, per index, a plurality of partially formed containers, a station comprising a plurality of devices arranged to perform substantially identical operations on a group of containers constituted by said plurality of partially formed containers, said indexing conveying device being arranged to advance said group through said station, and a controlling device arranged to cause said feeder to reduce to an integer the number of partially formed containers supplied, per index, to said conveying device. 
     According to a second aspect of the present invention, there is provided a method of handling partially formed containers, comprising feeding to an indexing conveying device, per index, a plurality of partially formed containers, advancing a group constituted by said partially formed containers through a station comprising a plurality of devices arranged to perform substantially identical operations on said group, and controlling said feeding, to reduce to an integer the number of partially formed containers supplied, per index, to said conveying device. 
     Owing to these two aspects, it is possible to provide apparatus for handling a partially formed container that can continue to operate at a diminished capacity after one of the devices of the apparatus fails to operate properly, and do so without producing defective containers such as uncapped (i.e. without pour spout fitments), unfilled, or unsealed containers. 
     According to a third aspect of the present invention, there is provided apparatus for handling partially formed containers, comprising a conveying device including a plurality of receiving portions for receiving partially formed containers, a plurality of stations arranged to perform operations on said partially formed containers, at least one of said stations comprising a heating device, and a controlling device arranged to control said conveying device, said conveying device being arranged to advance said partially formed containers through said stations and, following receipt thereby from said controlling device of a command to cease operation to halt said receiving portions such that they are offset from said heating device. 
     According to a fourth aspect of the present invention, there is provided a method for handling partially formed containers, comprising receiving a plurality of partially formed containers in a plurality of respective receiving portions of a conveying device, advancing said conveying device through a plurality of stations, performing at said stations operations on said partially formed containers, said performing including heating with a heating device said partially formed containers at least one of said stations, and displacing said receiving portions such that they are offset from said heating device, following receipt of said conveying device of a command to cease operation. 
     Owing to these two aspects, it is possible to provide apparatus for protecting partially formed containers from heat damage when the operation of the apparatus is stalled. No partially formed container should suffer heat damage, as it would be offset from the heating device. 
     According to a fifth aspect of the present invention, there is provided apparatus for homing a moving mechanical part, comprising a servo motor for driving said moving mechanical part, a controlling device controlling said servo motor, and a mechanical stop for stopping said moving mechanical part at a home position, wherein said controlling device is arranged to monitor servo motor power draw and to recognise said home position as corresponding to a position of said servo motor when said servo motor power draw reaches a predetermined value. 
     According to a sixth aspect of the present invention, there is provided a method of homing a moving mechanical part, comprising controlling a servo motor, driving said mechanical part by said servo motor, stopping said moving mechanical part at a home position by a mechanical stop, monitoring servo motor power draw and recognising said home position as corresponding to a position of said servo motor when said servo motor power draw reaches a predetermined value. 
     Owing to these two aspects, it is possible to provide a more precise home position reading and obviate the need to mount and maintain a separate sensor. 
     According to a seventh aspect of the present invention, there is provided apparatus for filling a partially formed container comprising a filler nozzle, a filler pump arranged to receive a product from a product reservoir and supplying said product to said filler nozzle, and a controlling device arranged to control said filler pump according to a selected one of a plurality of electronic cam profiles. 
     According to an eighth aspect of the present invention, there is provided a method of filling a partially formed container comprising receiving product from a product reservoir at a filler pump and supplying said product to a filler nozzle and controlling said filler pump according to a selected one of a plurality of electronic cam profiles. 
     Owing to these two aspects, it is possible to provide apparatus that includes at least two electronic cam profiles that can adapt filler pump operation. For example, the electronic cam profiles are selectable to adapt filler pump operation readily to suit different product viscosities. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In order that the invention may be clearly and completely disclosed, reference will now be made, by way of example, to the accompanying drawings, in which: 
         FIG. 1  is a side view of a container forming, filling and sealing machine, 
         FIG. 2  is a view similar to  FIG. 1  of the machine showing a different mode of operation, 
         FIG. 3  is a view similar to  FIGS. 1 and 2  of the machine showing a further mode of operation, 
         FIG. 4  is a screen shot of a control screen for the machine of  FIGS. 1 to 3 , 
         FIG. 5  is a side view of a turret and bottom folding, closing and sealing stations of the machine of  FIG. 1 , with mandrels of the turret shown in a mid-index position spaced between the stations, 
         FIG. 6  is an underneath view of a filler pump and pump servo motor of  FIG. 1 , 
         FIG. 7  is a top view of the filler pump and pump servo motor of  FIG. 6 , and 
         FIG. 8  is a cross-sectional view of the filler pump and pump servo motor of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a machine  2  for at least container forming and filling comprises a container feeder  4  which feeds partially formed, open-topped containers  6  to a conveying device  8 . The container feeder  4  includes a loader  10  supplying open container sleeves  6   a  to a rotating turret  12  having six radially extending mandrels  14 . The turret  12  is caused to rotationally index received container sleeves  6   a  through container bottom forming stations which fold, close and seal the container bottoms which will be discussed in more detail hereinafter. A container stripper strips the partially formed containers  6  from the mandrels  14  with suction cups into a transfer area where a transfer pusher pushes the partially formed containers  6  into container receiving portions in the form of container pockets  16  of the conveying device  8 . 
     The conveying device drive of the machine  2 , which is drivingly connected to the conveying device  8 , is commanded to index the partially formed containers  6  in a single-file serial arrangement through double-operation stations. Respective pairs of servomechanisms simultaneously perform identical operations on each partially formed container  6  of successive pairs of such containers in the single-file serial arrangement, as the conveying device  8  indexes a pair of partially formed containers  6  at a time, into each double-operation station. 
     The conveying device  8  is a double-indexing conveyor and the turret  12  is a single-indexing turret. The turret  12  operates at twice the speed of the conveying device  8 . With each conveyor index, a pair of serially arranged partially formed containers  6  is positioned at each of the double-operation stations. With each conveyor indexing motion the conveying device  8  is moved a distance equal to the width of two container pockets  16 . The controlling device indexes the container feeder  4  at  86  containers per minute and the conveying device at  43  containers per minute. 
     The first double-operation station that the partially formed containers  6  pass through is a top pre-breaking station  18  which includes a pair of top pre-breaking mechanisms for performing identical top pre-breaking operations on each of the pair of partially formed containers  6  at the pre-breaking station  18 . The second double-operation station that the partially formed containers pass through is a filling station  20  which includes a pair of fillers  22  for performing identical filling operations on each of the pair of partially formed containers  6  at the filling station  20 . The filling station  20  is discussed in more detail below with reference to  FIGS. 6 to 8 . The filling station  20  also includes a pair of container lifters disposed beneath the conveying device  8  and which serve to lift the partially formed containers  6  at the filling station  20  up to the fillers  22 . 
     A controlling device operates the machine  2 . The controlling device is connected to the container feeder  4  and is programmed to command the container feeder  4  to feed the partially-formed containers  6  to the conveying device  8 . The controlling device is also programmed to command the conveying device drive, that is drivingly connected to the conveying device  8 , to index the containers to the double-operation stations  18  and  20 . The mechanisms of the double-operation stations  18  and  20  which perform identical operations include a pair of servomechanisms or servo axes that simultaneously perform the identical operations on each partially formed container  6  of successive pairs. The controlling device is programmed to index the conveying device  8  only once for every two partially formed containers  6  that the controlling device commands the container feeder  4  to feed onto the conveying device  8 . 
     The controlling device is further programmed to detect down-line faults in either of the two servomechanisms of the pair of servomechanisms at each double operation-station  18  and  20 , and, in response, to display the fault information in graphical format on a screen, and to automatically shut down machine operation. The controlling device is also programmed, in response to the detection of a fault in either of the two servomechanisms at either of the double-operation stations  18  or  20 , to command machine operation in an over-ride mode. 
     In the over-ride mode, the controlling device shuts down machine operation and, when prompted by a machine operator (or automatically), commands the feeder  4  to operate without feeding partially formed containers  6  onto the conveying device  8  in positions that would otherwise be operated upon by whichever servomechanism of the double-operation station  18  or  20  is faulted. This allows the remaining servomechanism at the double-operation station to continue performing operations on the partially formed containers  6  and allows the machine  2  to continue to operate at half capacity without wasting containers. In other words, the over-ride mode makes use of a redundancy inherent in the double-operation configuration of these stations and allows continued operation despite the failure of any one of their dual servomechanisms. The pairs of servomechanisms may include a pair of cap applicators. 
     The controlling device is configured to be connected to each servomechanism of the pairs of servomechanisms disposed at the double operation stations  18  and  20  and is programmed to disable each servomechanism of the pairs of servomechanisms disposed at the double operation stations  18  and  20  that would otherwise be performing operations on empty positions along the conveying device  8  to save energy and reduce component wear. 
     The controlling device is further configured to be connected to the loader  10  and a turret drive of the feeder  4  where the turret drive is drivingly connected to the feeder turret  12  and is configured to rotate the turret about a horizontal turret axis. The controlling device is programmed to command the loader  10  of the feeder  4  to load the container sleeves  6   a  on the six radially-extending mandrels  14  of the feeder turret  12  positioned to receive container sleeves  6   a  from the loader  10 , and is further programmed to command the turret  12  to rotationally index the received container sleeves  6   a  through a plurality of bottom forming stations. 
     The controlling device is further programmed, when detecting a fault in any servomechanism of the pairs of servomechanisms, following machine shut-down and either automatically or when prompted by a machine operator, to disable the bottom forming and handling devices from operating on unoccupied mandrels  14 . The disabled forming and handling devices include a bottom breaker, the reciprocal motion of a bottom heater in and out of each container sleeve  6   a  as driven by a solenoid-controlled air cylinder, and bottom pressure applicators. While the motion of the bottom heater is disabled, the heater remains heated throughout over-ride operation. 
     The controlling device is also configured to be connected to the container stripper and is programmed to command the container stripper to engage each partially formed container  6  on a suction cup of the container stripper and to draw each partially formed container  6  downwards from each turret mandrel  14  to the container transfer area when each turret mandrel  14  reaches the container stripping station at a six o&#39;clock position of the turret. When detecting a fault in any servomechanism of the pairs of servomechanisms at one of the double operation stations  18  or  20 , the controlling device is programmed to disable the container stripper from operating on unoccupied mandrels  14 . 
     The controlling device is also configured to be connected to the transfer pusher and is programmed to command the transfer pusher to push the partially formed, open-topped containers  6  from the transfer area into respective adjacent pockets  16  of the conveying device  8 . When detecting a fault in any servomechanism of the pairs of servomechanisms at either of the double-operation stations  18  or  20 , the controlling device is programmed to disable the transfer pusher from operating when no partially formed container  6  will be present in the transfer area to save energy and to reduce wear and tear on these components. 
       FIG. 2  shows the machine  2  of  FIG. 1  operating following detection of a fault in the filler  22   a . The controlling device controls the feeder  4  to supply open container sleeves  6   a  only to alternate mandrels  14  of the turret  12 . As a result of the reduced supply of container sleeves  6   a  to the turret  12 , there is a reduction in the number of partially formed containers  6  supplied to the conveying device  8 . The double-indexing conveying device  8  of  FIG. 2  receives a single partially formed container  6  per index. 
     As can be seen in  FIG. 2 , when the index of the conveying device  8  reaches the filling station  20 , a partially formed container  6  is present adjacent the filler  22   b , but no partially formed container  6  is brought adjacent the faulty filler  22   a .  FIG. 3  shows the machine  2  of  FIG. 1  operating following detection of a fault in the filler  22   b.    
     When a fault is detected in any of the servomechanisms of the servomechanism pairs disposed at either of the double operation stations  18  or  20 , for example, the pair of top pre-breakers at the top pre-breaking station  18  or the pair of fillers  22  at the filler station  20 , machine operation may be shut down in response. The fault information is displayed in graphical format on a human user-machine interface in the form of a screen  24 , shown in  FIG. 4 , to an operator. The operator can decide whether to repair the machine or over-ride the fault. If the operator decides that he wants to over-ride the fault, he then presses a screen button  26  that causes the controlling device to command machine operation in the over-ride mode. 
     This generates a specific signal to the controlling device to control the feeder  4  to operate without feeding partially formed containers  6  onto the conveying device  8  in positions that would otherwise be operated upon by the servomechanism having the detected fault, allowing the remaining servomechanism at the same double-operation station to continue performing operations on partially formed containers  6 . The machine  2  continues to operate at half capacity without producing any empty or partially-formed containers  6 . Also disabled are each servomechanism of the pair of servomechanisms disposed at the other double operation station that would otherwise be performing operations on empty positions of the conveying device  8 . The forming and handling devices and the container stripper are disabled from operating on unoccupied mandrels  14 , and the transfer pusher is disabled during indexing periods when no partially formed container  6  will be present in the transfer area. 
     The machine  2  can also be configured to operate, when responding to a detection of a fault, automatically to reduce the number of partially formed containers  6  per index of the conveying device  8 . In this case, the fault is the specific signal sent to the controlling device to control the feeder  4  to reduce the number of container sleeves  6   a  supplied to the mandrels  14 . 
     The screen  24  allows the operator to control other aspects of the functioning of the machine  2 . Buttons  28 ,  30  and  32  allow the operator to control aspects of the machine  2  according to the container type being supplied by the feeder  4 . Button  28  indicates that a partially formed container  6  constructed from paperboard with a thin layer of polyethylene on either side is being supplied. Button  30  indicates that a partially formed container  6  that includes an aluminium barrier layer is being supplied and button  32  indicates a partially formed container  6  with an EVOH layer. The container type selector buttons  28 ,  30  and  32  change the temperature of the heaters of the bottom and top sealers. 
     Buttons  34 ,  36  and  38  are used to select the operation of the fillers  22  according to the viscosity of the product to be dispensed to the partially formed containers  6 . Button  34  selects a filling function appropriate to a product of a high viscosity, such as yoghurt, button  36  selects medium viscosity and button  38  selects low viscosity. Buttons  34 ,  36  and  38  cannot be used when the machine  2  is actively filling. 
     Various function buttons are disposed along the bottom of the screen  24 . Button  40  is a main menu button, button  42  is a back button, button  44  selects production mode, button  46  requests product to be supplied to the machine  2  and button  48  selects maintenance mode. Button  50  supplies current production data, for example the number of partially formed containers processed, button  52  is an alarm button, button  54  is a safety button, button  56  displays any servo motor faults and button  58  is a clutch page. Button  60  is a password button, and button  62  overrides the operation of the lifter servo motor. The lifter servo motor lifts the partially formed containers  6  prior to being filled at the filling station  20 . For some sizes of containers and/or product, the lifting of the containers is overridden. 
     Each filler  22  of the filling station  20  comprises a filler nozzle, a filler pump arranged to receive a product from a product reservoir and supplying said product to said filler nozzle, and the controlling device is arranged to control said filler pump according to a selected one of a plurality of electronic cam profiles. The controlling device is programmed to operate a pair of piston-type filler pumps that are in fluid communication with a product reservoir on respective inlet sides of the pumps, and with filler nozzles on respective outlet sides of the pumps, causing the pumps to draw product from the product reservoir and to dispense product received from the product reservoir through the respective filler nozzles. 
     The conveying device  8  carries the partially formed, open topped containers  6  in a single-file serial arrangement through the filling station  20 , pausing when each pair of partially formed containers  6  in the single-file serial arrangement is disposed at the filling station  20  in a position to receive product from the pair of filler nozzles. The controlling device also includes three operator-selectable filler cams having respective profiles that adapt the filler pump operation to the three different product viscosities. Consequently, the machine can be readily adapted to the dispensing of different products having different viscosities. 
     The filler cams are electronic cams programmed into a machine-readable program storage device. Filler cams selected for higher viscosity products such as yogurt are designed to operate the filler pump at correspondingly lower velocities to avoid breaking-down the viscosity of the product. Filler cams selected for higher viscosity products are also designed to increase dwell time between a pump pre-fill/pulling stroke that draws fluid from the product reservoir and a pump filling/pushing stroke that propels fluid through the nozzle. The increased dwell time helps to prevent more viscous products from dripping. 
     The controlling device also includes an operator interface that allows a machine operator to command the controlling device to change between the three different filler nozzle cam profiles of the filler nozzle cam profiles. The operator interface includes the graphical user interface displayed on the screen  24 . As discussed, above, the operator interface includes three screen buttons labeled low viscosity, medium viscosity, and high viscosity that can be used to select and cause the controlling device to use one of three corresponding filler nozzle cam profiles. 
     The container lifters, which are controlled by a servo motor, follow a motion profile that is determined by an electronic cam, in the same way that the filler servo motor follows a motion profile that is determined by an electronic cam. The cam profile for the container lifters that lift up the partially formed containers prior to and during filling can be user selected, again according to the viscosity of the product being dispensed by the fillers  22 . 
       FIG. 5  shows in more detail the turret  12  with the radially extending mandrels  14 . The controlling device is connected to and is programmed to operate a turret drive that is drivingly connected to and rotationally indexes the turret  12  supported for rotation about a horizontal turret axis. The turret&#39;s six radially extending mandrels  14  are positioned to receive open container sleeves  6   a  from the feeder  10  and to carry the received sleeves  6   a  through a series of work stations including a bottom breaking station  64 , a bottom end heating station  66 , a bottom tucker  68 , bottom end sealing and pressing stations  70  and  72 , and a stripping station (not shown). 
     The container bottom end heating station  66  includes an electric resistance bottom end heating element that is supported on a reciprocating carrier and is continuously heated to 500° C. when the machine  2  is operating, except that the station  66  is unpowered during emergency stops. The heating element heats the partially folded paperboard bottom end flaps of the container sleeves  6   a  to the point where a heat-sealable substance coating of the paperboard flaps is softened for subsequent end closure and sealing. The heat sealable substance may be a thermoplastic substance such as low density polyethylene (LDPE), possibly with the interposition of an oxygen barrier layer, for example aluminium or ethylene vinyl alcohol (EVOH). 
     The controlling device pauses each turret mandrel  14  at each station so that respective operations can be performed on the partially-formed containers  6  at each station. When the turret pauses a mandrel  14  at the heating station  66 , the reciprocating carrier advances the heating element to a position close to an axial outer end of the mandrel  14 . At each of the two succeeding bottom end pressure stations  70  and  72 , a bottom end pressure applicator advances radially inward to press the bottom end flaps together causing the softened heat-sealable substance is caused to form a seal across the container bottom end and to physically bind the bottom end flaps together into a single container bottom end panel. 
     The controlling device also operates the stripper that includes a suction cup mounted on a vertically reciprocating carrier. When this carrier is extended upward, the suction cup engages whatever partially formed container  6  the turret  12  has positioned at the stripping station, i.e., at a six o&#39;clock position of the turret  12 . This carrier is then retracted, drawing the partially formed container  6  downward from the respective mandrel  14  to a container transfer area. The controlling device is also programmed to operate a transfer pusher that pushes the partially formed containers  6  from the transfer area to the conveyor  8 . 
     The controlling device is connected to and receives commands from a control screen. A machine stop command is issued to the controlling device by actuating, during machine operation, a stop button or a “feed” button displayed on the control screen. In response to such a machine stop command, the controlling device halts turret rotation but leaves the bottom end heating element of the station  66  in a heated state so that the element will be ready to quickly resume operations. To prevent container heat damage that would otherwise occur from being positioned for an extended period of time at the bottom end heating station in radial alignment with the bottom end heating element, the controlling device stops the turret at a mid-index position in which the mandrels are disposed between stations. The stopping of the turret  12  is an automatic process and the machine  2  enters idle mode within ten seconds of emptying. 
     The controlling device also stops the feeder  4  in response to a machine stop command so that containers will not be wasted as the machine continues to run during a subsequent stop period. The stop period is a period of approximately 10 seconds during which the controlling device allows the turret  12  and conveyor  8  to continue indexing to insure that no partially formed containers  6  are left in the machine  2 . 
     The controlling device stops operations at each station in response to a machine stop command and after the last container passes. After receiving a machine stop command and after the last container has cleared the machine the controlling device clears a shift register and then, two seconds later, stops the conveyor  8 . 
     The controlling device is programmed to re-align the turret from a mid-index stop by commanding the turret drive to move the turret from its half-index position to a normal index position synchronized with a machine virtual axis. A restart command is issued by actuating a restart button displayed on the control screen. 
     In practice, partially formed containers in the machine  2  can be protected from heat damage when machine operation is stalled by programming the controlling device to stop the turret at a mid-index position in response to a machine stop command and issuing a machine stop command by pressing either the stop button or the feed button on the control screen. This will also stop the feeder  4  but the turret  12  and conveyor  8  will continue indexing for a 10 seconds to insure that no partially formed containers  6  are left in the machine, and the bottom end heating element will remain in a heated state. After the last finished container passes out of the machine, the controlling device&#39;s shift register will clear and then, two seconds later, the conveyor  8  will stop. To restart the machine, a machine operator actuates the restart button displayed on the control screen which causes the controlling device to re-align the turret by commanding the turret drive to move the turret from its half-index position to a normal index position synchronized with a machine virtual axis. 
       FIGS. 6 ,  7  and  8  show in more detail part of a filler  22  of the filing station  20  of the machine  2 . A filler pump piston  72 , of a pump  78 , is supported for reciprocal motion in a cylinder  74  and a mechanical stop  76  is positioned in the cylinder  74  in a position to halt the piston  72  in a home position within the cylinder  74 . The filler pump  78  is disposed at the filling station  20  and is in fluid communication with a product reservoir on an intake side  80  of the pump  78  and with filler nozzles on an output side  82  of the pump  78 . The filler pump  78  is configured to draw product from the reservoir and to dispense product received from the product reservoir through the filler nozzle. Product is dispensed from the filler nozzle into a partially formed container  6  each time the conveying device  8  positions a partially formed container  6  in a position to receive product dispensed from the nozzle. 
     The filler pump piston  72  is reciprocally driven within the cylinder  74  by a rotary servo motor  84  through a servo linkage  86 , the rotary reciprocal motion of the servo motor being commanded by the controlling device. 
     The mechanical stop  76  within the cylinder  74  (which can be formed as part of the cylinder) is used to determine a home position of the filler  22  when synchronisation of the various parts of the machine  2  is required. The normal working stroke of the piston  72  does not reach the stop  76 , but when a homing programme is started, the servo motor  84  operates to extend the stroke of the piston  72  until the stop  76  is engaged by the cylinder  74 . The controlling device is programmed to recognize the home position of the piston  72  as corresponding to the rotary position of the servo motor  84  when rotary servo motor power draw reaches a predetermined value. 
     In practice, the homing is accomplished by providing the mechanical stop  76  positioned to halt the motion of the piston  72  in a home position and recognizing the home position of the piston  72  as corresponding to the position of the servo motor  84  when power draw from the servo motor  84  reaches a predetermined value of 20% above a maximum power draw value (rated power value). The predetermined value, for greater accuracy, is preferable equal to 30% of the maximum motor power draw value. In other embodiments any suitable predetermined value may be used so long as it is high enough to prevent transitory power draw spikes from being mistaken for the homing of a part such as the piston  72 . 
     SEQUENCE LISTING 
     Not applicable.