EP1660394A1

EP1660394A1 - Rotary transfer mechanism

Info

Publication number: EP1660394A1
Application number: EP04743685A
Authority: EP
Inventors: Warren George Smith; Keith Robert Coveney
Original assignee: Bradman Lake Ltd
Current assignee: Bradman Lake Ltd
Priority date: 2003-08-20
Filing date: 2004-08-11
Publication date: 2006-05-31
Also published as: WO2005019074A1; GB0319598D0

Abstract

The present invention relates to a rotary transfer mechanism for transferring an object, such as a carton, from an object holder to a receiving station. The rotary transfer mechanism has a drive shaft (15) rotateably mounted on a support (5) and a carrier (10) rotatable with the drive shaft. A first drive (17) is coupled to the drive shaft (15) for rotating the carrier (10) relative to the support (5). At least one feeder arm (30) is mounted to the carrier (10) and has at least one suction device (32) for releaseably engaging an object to be transferred. The rotary transfer mechanism also has a second drive (47), which is coupled to the at least one feeder arm (32) and independent of said first drive (17). Preferably the drives, (17, 47) are coupled to respective independent servo-motors. As the drives are independent from each other the flight path of the at least one feeder arm and suction device is not determined solely by the first drive, but can be varied according to the relative speed and phase of the two independent drives. In this way much more control of the flight path is possible and a wider range of flight path profiles can be achieved.

Description

Rotary Transfer Mechanism TECHNICAL FIELD The present invention relates to a rotary transfer mechanism for transferring an object from an object holder to a receiving station. It is particularly, but not exclusively, applicable to a mechanism for flat objects and objects having a flat surface, especially cartons. Rotary transfer mechanisms are often known in the art as "rotary feeders".

BACKGROUND ART In general rotary feeders have one or more feeder arms bearing suction cups configured to apply suction to pick up an object from an object holder at one point in their flight path and to release said suction to deposit the object at a receiving station at another point on their flight path. The suction cups are carried through their flight path by the feeder arms that are attached to a rotating carrier. In addition the feeder arms, and therefore the suction cups they carry, are rotatable relative to the carrier. Therefore the flight path of the suction cups is the sum of the rotational motion from the carrier and the rotation of the feeder arm relative to the carrier. In one known arrangement, described in US 2915308, a stationary sun gear is concentric with the drive shaft of the carrier and planetary gears fixed to the carrier idle on the stationary sun gear. The planetary gears each engage with a respective outer gear also mounted on the carrier and each outer gear is fixed to and coaxial with a respective feeder arm. Thus when the carrier is rotated the planetary gears rotate by engagement with the stationary sun gear causing the outer gears and thus the feeder arms and attached suction cups to rotate. The suction cups thus follow a predetermined path that is the sum of the rotary motion of the support arm about its own axis and the orbiting of the support arm about the drive shaft.

This predetermined path is inflexible and fixed by the relationship of the various gears. The shape of the path for one of the suction cups on the above-described type of rotary feeder is shown in Fig 11. The path has three nodes (turning points) ; the object supply has to be placed at one of these nodes, so that objects can be picked up, and the receiving station at another of these nodes so that the objects can be placed there.

EP 0331325 discloses a rotary feeder for cartons. Each carton is stored in flat form in a dispensing magazine and opened out or "erected" into its expanded form (in which it is able to receive contents) during placement of the carton on a receiving station on a conveyor. However there is no system of sun and planetary gears for regulating rotation of the feeder arms relative to the carrier. Instead, each feeder arm is fixed to a coaxial pinion having a cam follower. Rotation of the pinion and hence the support arm relative to the carrier is determined alternately either by engagement of the pinion with an arcuate rack mounted on a stationary support or engagement of the cam follower with a cam track also mounted on a stationary support.

The cam track can cause the suction cups (attached to the support arm) to follow a path with node points at different locations to those possible with a sun- planetary gear system. The cam track also makes it possible for the path of the suction cups to travel in the same direction as the conveyer for a limited period while the carton is being deposited. However the path of the suction cups is, as with the above-described sun- planetary gear mechanism, fixed by the parts used and can only be changed by physical adjustment of the parts (e.g. by replacement of the cam track) .

SUMMARY OF THE INVENTION At its most general one aspect of the present invention proposes that the rotary transfer mechanism is provided with a second drive for driving rotation of at least one feeder arm, said second drive being independent of a first drive means for driving rotation of the carrier which carries the feeder arm. As the second drive means is independent of the first drive, the flight path of suction device attached to the feeder arm is not predetermined by the first drive because it depends on the second drive as well. Therefore a wide range of different suction device path profiles can be generated depending on the relative phasing of the first and second drive. Phasing' means the relative speeds, direction of driven rotation etc of the drives. Such an apparatus is easy to adapt to different objects (e.g. different sizes of carton blanks made from board or other materials) without the need for any major modifications. The necessary parameters to give a flight path suitable for a particular object may be stored in a program in the memory of a controller, so that the appropriate program can be selected by a user making the apparatus easy to use with different objects.

Thus, a first aspect of the present invention may provide a rotary transfer mechanism for transferring objects from an object holder to a receiving station, comprising: a first drive shaft rotably mounted on a support, a carrier rotatable with said first drive shaft, a first drive coupled to said first drive shaft for rotating the carrier relative to said support; at least one feeder arm attached to and extending outwardly from said carrier so that the feeder arm is arranged to orbit said first drive shaft when the carrier is rotated; said feeder arm being rotatable relative to the carrier and having at least one suction device for releasably engaging an object to be transferred; and a second drive for driving rotation of said at least one feeder arm, said second drive being coupled to said at least one feeder arm and independent of said first drive .

The object holder and receiving station are not part of the rotary transfer mechanism, but are the locations at which the rotary transfer mechanism picks up the objects and subsequently deposits them. The object holder may simply be a surface bearing the objects to be transferred, but usually will be a magazine or hopper type device for dispensing the objects. The receiving station may be a stationary surface or compartment for receiving the objects, or could be a moving surface such as a conveyer. The conveyer may have a plurality of divisions along its length each constituting a receiving station (i.e. it may be ^Λflighted' ) .

The drive may be a motor or a means for transferring or imparting rotational motion from a motor. For example the drive could be a chain or pulley for transferring rotational motion from a motor to a drive shaft.

The suction device preferably comprises a suction cup. Preferably there is a vacuum system for placing the suction device alternately in communication with a vacuum and the atmosphere. Preferably a controller of the rotary transfer mechanism is configured to control the mechanism such that the suction device is placed in communication with the vacuum from at least the point of the flight path where the suction device is adjacent the object holder (so that it can contact an object to be picked up) to the point of the flight path where said suction device is adjacent the receiving station on which the object is to be deposited. Preferably said controller is configured to control the mechanism such that the suction device is placed in communication with the atmosphere at the point in the flight path of the suction device where it moves away from said receiving station (after depositing and where appropriate also erecting said object) . This control may be achieved by rotary valves, computer controlled valves, sensor controlled valves or other suitable means as will be apparent to a person skilled in the art.

Preferably, but not necessarily, at least one of the drives is a servo-motor or is coupled to a servo-motor. Most preferably each drive is a servo-motor or is coupled to a respective servo-motor. A separate (independent) motor is needed for each respective drive so that the drives are independent from each other.

As the speed and direction of rotation of a servo motor can be changed this allows the phasing of the various drives to be conveniently changed to achieve different flight path profiles for the suction device (s) without replacing the motors themselves or without dissembling and rearranging the apparatus or making other mechanical adjustments. This makes the rotary transfer mechanism flexible. For example, different suction device path profiles may be needed depending on the size and type of the objects to be transferred.

Furthermore provision of one or more servo-motors allows the phasing to be adjusted in real time according to the desired profile at a particular point in the cycle. Thus for certain objects (e.g. cartons) it may be desirable to vary the flight path profile depending on whether the suction device is picking up an object from the object holder or depositing an object at the receiving station. This can be achieved for example by speeding up or slowing down one or more of the drives for part of the cycle. The throughput of a rotary transfer mechanism can be measured by the number of objects transferred from the object holder to a receiving station in given period of time. This is dependent on the speed of the carrier, but also on the number of feeder arms. Thus while the above has mentioned at least one feeder arm and a first and second drive, there may be a plurality of feeder arms. There may optionally also one or more further drives (independent of the other drives and preferably each being a respective servo-motor or being coupled to a respective servo-motor) coupled to one or more of the feeder arms so that several feeder arms can be controlled independently of each other.

In general each feeder arm should be coupled to only one of the second or further drives (and optionally also to the first drive, e.g. via the carrier if a planetary gear system is used as discussed below) . This keeps the mechanism simple and allows feeder arms coupled to different drives to be moved independently of each other. For example, there may be a plurality of feeder arms and a third drive coupled to one or more feeder arms which are not coupled to the second drive, said third drive being independent of both said first and second drives.

Preferably the second drive is coupled to more than one feeder arm. This allows more than one feeder arm to be controlled by one drive thus keeping down the cost of the mechanism (especially where servo-motors are used) . Where there are one or more further drives, any of the further drives may be coupled to more than one feeder arm in a similar manner so as to introduce redundancy and reduce costs. This is discussed in more detail a bit later.

Preferably the at least one feeder arm is coupled to the second drive by a sun gear and planetary gear system. If there are several feeder arms then preferably each feeder arm is coupled to either the second or one of the further drives (if there are further drives) by a system of sun and planetary gears. This allows for relatively precise control of the motion of each feeder arm.

In one possible configuration the planetary gears may be rotably mounted on the carrier and coupled to a sun gear driven by the second drive, in which case the at least one feeder arm is coupled to both the first and second drives via the carrier and the sun gear respectively. The coupling of the planetary gear(s) to the sun gear may be by any appropriate means, such as engagement, meshing engagement, chain and track or other means as is well known in the art. The coupling of the planetary gear(s) to the feeder arm (or where there is more than one feeder arm, respective feeder arms) may be by fixed attachment (coaxial or otherwise) , or via one or more further (e.g. outer) gears coupled to the planetary gear(s). Coupling of the planetary gear(s) to further gear(s) may be by any of the means discussed above.

Each drive may drive a respective drive shaft. If a sun and planetary gear system is used then each drive shaft may have a sun gear for coupling with one or more planetary gears coupled to the feeder arms (except the first drive shaft which need not have any sun gear as it is for driving rotational motion of the carrier relative to the support) .

Conveniently the drive shafts may be provided as a system of shafts one inside the other and idling on each other, e.g. via ball bearings or the like, so that the drive shafts are coaxial but able to rotate independently of each other. Preferably the shafts are concentric with one another. This allows the rotary feeder to be made relatively compact despite the presence of several drives. Where sun gears are used, the sun gears and carrier are each attached to a different shaft and can be axially spaced apart from each other.

Preferably the feeder arms are attached to the carrier by crank members pivotably mounted to the carrier. Preferably the feeder arms are pivotably mounted to the crank members. This allows for an extra degree of rotational freedom and therefore more flexibility in the flight path of the suction device (s) . The feeder arm is then able to rotate about both its own axis and the axis of the crank's pivotal attachment to the carrier as well as along with the general motion of the carrier. In other words the feeder arm has two degrees of rotational freedom relative to the carrier.

Preferably there is a cam track and each feeder arm is coupled with a respective cam follower engageable with the cam track for controlling rotation of the feeder arm relative to the carrier when in use the carrier rotates. This facilitates further control of the feeder arms via the cam track. In addition where more than one feeder arm is driven by the same sun gear/drive, while the sun gear induced rotation is the same for all feeder arms driven by that sun gear at a given point in time, the rotation by the cam track is different at each point in the cycle as determined by the cam track at that point in the cycle (the position in the cycle being measured by the number of degrees the carrier has rotated out of 360°) .

Preferably the cam followers are coupled to the feeder arms via respective crank members pivotably attached to the carrier. With this configuration the cam follower/cam track arrangement controls rotation of the crank arm relative to the carrier, while the coupling of the second (and any further drives) to the respective follower arm(s), e.g. by a planetary and sun gear arrangement, controls rotation of the follower arm about its own axis.

The applicant has realised that the path of each feeder arm (and suction device attached thereto) has a critical range (from the approach to the object holder to just after depositing of the object - and in the case of a carton, erecting of the carton - on the receiving station and a non-critical range (the other parts of the flight path) .

Therefore where two feeder arms are coupled to the second drive, it is preferable that they are spaced apart by an amount equal to or greater than this critical range (e.g. at least as much as the angle subtended by the object holder and the receiving station on the first drive) . Most preferably they are attached to opposite sides of the carrier. In this way the second drive can be controlled to give the desired path profile for the suction device of either feeder arm in its critical range and it is not necessary to worry about the ramifications that this control will have on the suction device on the other feeder arm that feed arm's suction device will be in the non-critical range.

The same applies to two feeder arms coupled to a third or other additional drives. Where there are more than two feeder arms coupled to a second or further drives then, on the above principle they should where possible be spaced apart by an amount equal to the critical range. They may be spaced apart as far as possible, e.g. equally spaced around the carrier.

Preferably there is a controller having at least one program for controlling said feeder arm or arms to perform predetermined paths around the first drive shaft when in use the carrier is rotated by the first servomotor. The controller may effect this control by controlling the first drive, the second drive and any further drives to give the desired suction device path profiles .

The controller may have several preset programs and means for allowing an operator to select the appropriate program for the job at hand (e.g. according to the type, size and shape of the objects to be transferred, the location of receiving station and object holder etc. The controller may have means for adjusting the programs, editing the programs etc so that a user can vary the programs according to his particular needs.

The above-described mechanism allows flexibility in the path of the suction device (s) . Various possible desirable characteristics of the path will now be described. It is preferable, although not essential, that the rotary transfer mechanism is configured to provide a suction device path profile having one or more of the desirable characteristics outlined below. This may be achieved for example by setting the mechanism to operate in a particular way, coordination of the respective drives, and/or using an appropriate program in the controller.

It is preferable that the suction device approaches the object holder in a linear motion (e.g. substantially perpendicular to the, usually flat, object to be picked up) . This helps to create a better seal and reduces wear of the suction device, compared to a situation where the suction device roll into the objects (e.g. cartons) when picking them up from the object holder.

It is preferable that the suction device moves away from object holder in a linear motion (e.g. substantially perpendicular to objects held in the holder) after picking up an object from the object holder. This is better than the suction device rolling immediately after picking up an object from the object holder, because such rolling can cause the object to rotate into any remaining objects in the object holder and consequently to bend and buckle or damage the remaining objects. Furthermore, if the object is a carton, moving away in a linear path should reduce the possibility that the carton will spring open and resonate just after being extracted from the object holder.

It is often the case that a rotary feeder is required to transfer an object to a receiving station on a (moving) conveyor. In this case it is preferable for the suction device to move along with the conveyer in the same direction as the conveyer for a portion of its flight path during which it deposits the object on the conveyer. This is better for example than the suction device travelling towards and away from the receiving station very quickly (as e.g. in Fig 11) .

When the object is a carton it is usually erected against a side wall of the receiving station (e.g. a lug extending across a conveyer) . Adjustment of the flight path enables the rotary feeder to cope with different sizes of carton. For a given path profile the actual angle of attack at which the carton contacts the sidewall will vary depending on the size of the carton. However, there is an optimum angle of attack. Therefore it is preferable that the speed of rotation of the feeder arm is varied according to the size of the carton so that the desired angle of attack is achieved. This may be achieved by varying the relative speed of the drives (e.g. varying the speed of the first or second drive) . For example, while it is necessary for the feeder arm to complete a given (integer) number of revolutions for every cycle of the carrier it is possible for the speed of its rotation to be varied around the cycle so that it can be speeded up or slowed down over a particular range so that the suction device (or the carton held by it) has a desired angle relative to the receiving station side wall at a particular point in the cycle. Thus the angle of attack can be set to a desired angle which may be varied by control of rotation of the feeder arm relative to the carrier. The optimum angle of attack is currently thought to be 15 to 20 degrees between the carton in its flat un-erected state and the sidewall of the receiving station. It is preferable that after depositing the object at the receiving station the feeder arm rotates relative to the carrier in such a way as to direct the suction device away from the receiving station. This helps to keep a suction device performing a return path (i.e. in the uncritical' range) from interfering with an object carried by an adjacent suction device in the critical range (e.g. incoming to the receiving station). If the feeder arm continued rotating in the same direction as it was prior to depositing the object then it would most likely point towards the incoming suction device and might interfere with them. Thus the feeder arm can be controlled to rotate in a first direction just prior to depositing an object at the receiving station and to rotate in a second direction opposite the first direction just after depositing said object.

The present system may make it possible to provide a path profile having all of the above characteristics due to the independent drives and other features of the mechanism described above. It is particularly advantageous to combine the preferred features. For example where the mechanism comprises both a cam-follower cam track system and sun and planetary gear system, this may be used to advantage by controlling one of the drives to counteract undesired rotation of one of the feeder arms produced by the cam-follower and cam track system at a given point in the cycle by counter rotation of the planetary gear coupled to said feeder arm.

Further aspects of the present invention may provide a method of transferring objects (e.g. cartons) from an object holder to a receiving station by using a rotary transfer mechanism comprising a rotatable carrier, one or more feeder arms rotably attached to said carrier and having a suction device for releasably engaging the object to be transferred and controlling the carrier and said feeder arm or arms and suction devices to follow a flight path, preferably having one or more of the above described desirable flight path characteristics.

The flight path may have any combination of the above described desirable flight path characteristics,

The rotary transfer mechanism in this method may have any of the features of the rotary transfer mechanism according to the first aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the present invention will now be described with reference to the accompanying drawings in which : Fig. 1 is a perspective view of a rotary transfer mechanism; Fig. 2 is a partial perspective view of a rotary transfer mechanism with a cut away section showing the internal workings of the mechanism; Fig. 3 is a side view of the rotary transfer mechanism; Fig. 4 is a plan view of a feeder arm of the rotary transfer mechanism; Fig. 5 is a perspective view of a crank arm, gear wheel and cam follower assembly for use in the rotary transfer mechanism; Fig. 6 is a plan view of one face of the assembly of Fig. 5; Fig. 7 is a side plan view of the assembly of Fig. 5; Fig. 8 is a plan view of a cam track; Fig. 9 shows a possible flight path of the suction device of the one of the rotary feeder arms in relation to the object holder and the receiving station; Fig. 10 shows the cam track super imposed on the flight path of Fig. 9; Fig. 11 shows the flight path of a suction device attached to the feeder arm of a conventional rotary transfer mechanism using a fixed arrangement of planetary gears and a stationary sun gear; Fig. 12 shows a further possible flight path of a suction device in a rotary feeder according to the present invention; Fig. 13 shows a further example of a possible flight path of the suction device of the rotary feeder according to the present invention; Fig. 14 is a schematic plan showing a rotary transfer mechanism and controller, and Fig. 15 is a graph showing speed of rotation of the first drive during part of the cycle.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT A rotary feeder or rotary transfer mechanism 1 according to an embodiment of the present invention is shown in Figs. 1 to 3. The rotary transfer mechanism comprises a support 5 to which a disk shaped carrier 10 is rotably mounted by means of a first drive shaft 15 which is fixably secured to the carrier 10. The first drive shaft 15 is coupled to a first drive 17 (see Fig. 3) for rotating the carrier 10 relative to the support 5. The support 5 has a plurality of apertures 5a to facilitate attachment to a packaging machine.

A plurality of feeder arms 30 are attached to the carrier 10 and extend outwardly from the carrier in a direction substantially parallel to the axis of the fist drive shaft 15. The feeder arms 30 are arranged around the carrier so that the feeder arms orbit the first drive shaft when the carrier 10 is rotated by the first drive 17. The feeder arm construction is shown in more detail in Fig. 4. Each feeder arm comprises a feeder arm shaft 31 and has a suction device, in the form of a pair of suction cups 32 attached to the feeder arm shaft 31. The suction cups 32 are fixedly mounted to the shaft 31 and extend laterally from it, so that when the feeder arm shaft 31 rotates the vacuum cups 32 describe circles around it. Each vacuum cup 32 is connected to a vacuum by way of vacuum pipes 35 which connect to a vacuum pump. The purpose of this vacuum system is to allow the vacuum cups to pick up and hold objects when a vacuum is applied and release them when it is not. Each feeder arm is attached to the carrier 10 in such a way that it is rotatable relative to the carrier. The rotary transfer mechanism 1 has a mechanism for controlling rotation of the respective feeder arms 30 relative to the carrier 10 and this is described in more detail later. For now it is to be noted that the flight path of a suction device 32 on a rotary feeder arm 30 is determined by the sum of the rotation of the carrier 10 relative to the support 5 and the rotation of the feeder arm 30 relative to the carrier 10.

Fig. 9 shows the flight path of a suction device 32 attached to a feeder arm 30 of the rotary transfer mechanism 1. The flight path has a first node A at an object holder 200 and a second node B at a receiving station 300 the object holder is a hopper containing cartons in flat-pressed form and has an opening for dispensing the cartons. The receiving station 300 is a section of a conveyor for transporting the cartons. The conveyor is divided into sections 310 by lugs 315 extending across the conveyor. Each section 310 forms a separate receiving station. The conveyor travels in the direction 311 to 312 in Fig. 9 and for clarity only a small section of the conveyor is shown in Fig. 9. The object holder 200 and receiving station 300 are 120° apart from each other with respect to the axis of the first drive shaft 15 of the rotary transfer mechanism 1. However, in other embodiments it would be possible have the object holder 200 and receiving station 300 separated by different amounts. The critical portion of the flight path where the suction device 32 positioning is especially important to achieve picking up, transfer, depositing (and if a carton erection) of the object is from point C to point B on the flight path of Fig 9.

A controller of the rotary transfer mechanism puts the suctions device 32 in communication with a vacuum produced by a suction pump (not shown in Figs. 1-3, 570 in Fig 14) when it is adjacent the object holder at node A and keeps the suction device 32 in communication with said vacuum as the suction device 32 moves towards node B. The suction device 32 thus picks up a carton from the object holder 200 and transports it to the receiving station 300. At the receiving station 300 the combined movement of the suction device 32 and the engagement of the flat carton with a lug 315 (usually the rear lug) of the receiving station on the moving conveyor causes the carton to erect. For example the carton opens out into a square or rectangular cross section so that it can receive contents to be cartoned. Once the carton has been successfully erected the controller puts the suction device 32 back in communication with the atmosphere so that the carton is released and allowed to travel with the receiving station along the conveyor. The suction device which is then no longer carrying the carton returns around the flight path to node A.

The on/off control of the vacuum in relation to the suction device is achieved by rotary valves. There is one rotary valve 19 for each feeder arm and this puts the suction device 32 on that feeder arm in communication with the vacuum via -vacuum pipes 35 at predetermined portions of the cycle corresponding to those discussed above. Alternatively the valves may be electronically controlled by a solenoid. The suction device is put into communication with the atmosphere by a separate release valve which can be controlled in a similar fashion. As the rotary valves 19 are mounted to the end of the rotary feeder arms the vacuum feed pipe (34) do not twist as the mechanism rotates.

The rotary transfer mechanism is mounted to a packaging machine by its support 5 which can be fixed at a suitable location on the packaging machine. For each incoming product the rotary transfer mechanism removes a flat carton from the object holder 200, erects it and places it on a receiving station on the conveyor.

The mechanism for controlling the rotation of the feeder arms 32 relative to the carrier 10 will now be described.

As can be seen in Fig. 3 the rotary transfer mechanism 1 has three drive shafts 15, 40 and 50 arranged coaxial with and idling on each other and having respective pulleys 16, 46 and 56 towards one end. The drive shafts 15, 40 and 50 are able to rotate independently of each other and are radially spaced apart by bearings or similar means.

The idling shaft system is mounted on and supported by the support 5. The drive shafts 16, 46 and 56 are rotatable relative to the support. The first drive shaft 15 is the central drive shaft and is fixed to the carrier 10 at one end so that when it rotates relative to the support the carrier 10 rotates also. It has a pulley (16) at one end which is coupled to a first drive 17. The second drive shaft 40 idles on the outside of the first drive shaft 15 and has a pulley 46 which is coupled to a drive 47. The third drive shaft 50 idles on the outside of the second drive shaft 40 and has a pulley 56 which is coupled to a third drive 57.

The drives 17, 47 and 57 are independent of each other and thus each of the first to third drive shafts 15, 40 and 50 can be made to rotate relative to the support 5 independently of each other (e.g. at different speeds and/or in different directions). In this embodiment each of the drives is a drive cord coupled to a respective servo-motor. The servo-motors are independent of each other. In alternative embodiments the drive shafts could be connected directly to the servomotors (in which case the servo-motors are effectively the rives' ) or coupled to the servo-motors by other means such as a chain and track system. It would also be possible to use a normal (non-servo) motor to drive one or more of the drives, although this would reduce the flexibility of the system.

A sun gear 42 (in this embodiment a large toothed gear wheel) is fixed to the second drive shaft 40 at the end near the carrier 10. This sun gear 42 engages with a planetary gear 44 (see Fig 1) which idles on the sun gear 42 and which is rotably mounted on the carrier 10. The planetary gear 44 engages with an outer gear 46 which is fixedly mounted on one of the feeder arm 30b and idles on the planetary gear 44. Thus when the second drive shaft 40 rotates relative to the first drive shaft 15 the planetary gear 44 is made to rotate due to its engagement with the sun gear 42. This causes the outer gear 46 to rotate and the feeder arm 30b to which the outer gear 46 is fixed thus rotates relative to the carrier 10. In this embodiment the outer gear 46 is coaxial with the feeder arm 30b and so the feeder arm is caused to rotate about its own axis. In alternative embodiments the outer gear 46 and the feeder arm 30b could be radially offset from each other (i.e. they need not have coincident axes) .

Thus the feeder arms 30b is coupled to the second drive shaft 40 by a sun and planetary gear system such that rotation of the second drive shaft 40 relative to the first drive shaft 15 causes the feeder arm to rotate relative to the carrier 10. The third drive shaft 50 has a similar system with sun gear 52 (see Figs. 2 and 3) fixedly mounted on the end near carrier 10, engaging with planetary gear 54 which is rotably mounted on the carrier and engages with outer gear 56. Outer gear 56 idles on the planetary gear 54 and is fixedly mounted to feeder arm 30a. Thus rotation of the third drive shaft 50 relative to the first drive shaft 10 causes feeder arm 30a to rotate relative to the carrier 10. As can be seen in Fig. 3 the sun and planetary gear systems of the second and third drive shafts are axially offset from each other so that they do not interfere with each other.

As shown in Fig 1 there are four feeder arms 30a, 30b, 30c and 30d. Feeder arm 30c is coupled to the third drive shaft 50 by a planetary gear and an outer gear coupled to the sun gear 52 as described above for the feeder arm 30a. Feeder arm 30d is coupled to the second drive shaft 40 by a planetary gear and outer gear coupled to the sun gear 42.

Thus feeder arms 30a and 30c are both coupled to the third drive shaft 50 (and therefore the third drive 57) . They are positioned on opposite sides of the carrier. This positioning has the advantage that the third drive can be controlled to give the desired flight path for the suction device 32 of the feeder arm 30a in the critical range from position C to position B of the flight path without undue concern about the consequent motion of the suction device 32 on the other feeder arm 30c coupled to it as this suction device will be outside the critical portion of its flight path and vice versa when feeder arm 30c is at the critical portion of its flight path.

Feeder arms 30b and 30d are both coupled to the second drive shaft 40 (and therefore the second drive 47) . They are positioned on opposite sides of the carrier, which has the advantage mentioned above. Rotation of the feeder arms 30 due to the sun and planetary gear systems described above gives the feeder arms 30 a first degree of rotational freedom relative to the carrier 10. Each feeder arm 30 is pivotably mounted to the carrier 10 by a crank member 60 which gives a second degree of rotational freedom.

Each crank member 60 is part of a respective crank assembly which can be best seen in Figs 5 to 7. The feeder arm 30 is rotably mounted to the crank member 60 at feeder arm receiver 61. This mounting of the feeder arm is rotatable so that the feeder arm can rotate about its own axis when driven by the sun and planetary gear system.

The crank member 60 is pivotably mounted to the carrier 10 at a location 62 spaced apart from the feeder arm receiver. The pivotable mounting can be by a pivot pin 63 mounted to the carrier 10 and extending into an aperture at location 62 of the crank member 60. The overall effect is that the feeder arm 30 is able to rotate about its own axis and also about the axis of the pivotal attachment of the crank member 60 to the carrier 10.

The pivot pin 63 extends through the carrier 10. On the feeder arm side of the carrier 10 it is pivotably attached to the crank member 60 as described above. On the other side of the carrier 10 it has an outer gear of the planetary gear system mounted on it (denoted in Figs 5-7 by reference numeral 56 but it is to be understood that the other feeder arms are attached in a similar manner to their respective crank members and outer gears) . The pivot pin 63 passes through the outer gear as well and bracket 70 is pivotably attached to it. The bracket 70 is part of a cam follower system and has a cam follower 72 fixed to it. The cam follower 72 extends into and engages with a cam track 80 which is mounted to or provided on the support 5. A plan view of the cam track 80 is shown in Fig 8. The cam follower 72 is forced to follow the cam track 80 as the carrier 10 rotates and this causes the crank member 70 to pivot about its pivotal attachment 62,63 with the carrier 10 due to forces transmitted via the assembly of the cam follower 72, bracket 70 and pivot pin 63. In this way rotation or pivoting of the feeder arm 32 about the axis of the crank member's pivotal attachment to the carrier 10 (i.e. in this embodiment about the axis of pivot pin 63) is controlled via the cam track 80. Thus the crank member and cam follower assembly shown in Figs 5 to 7 controls the second degree of rotational freedom of the feeder arm relative to the carrier 10 on the basis of the cam track 80. As the cam track path varies around the cycle, the control is exerted as a function of the position of the feeder arm in the cycle (a full cycle being a single revolution of the carrier) . The first degree of rotational freedom of a feeder arm is controlled by the sun and planetary gear system. Thus for any two feeder arms coupled to the same sun gear (and thus to the same drive) -e.g. arms 30a and 30c - this rotation will be the same for both arms at any given point in time. For the second degree of rotational freedom it can be different however, as this is controlled by the cam track 80 and so depends on the position of the feeder arm in the cycle (and the feeder arms are spaced apart and therefore at different positions in the cycle) . In this way undesired rotation relative to the carrier 10 due to the sun and planetary gear system can be counteracted by the cam track (or vice versa) by appropriate design of the cam track and/or control of the appropriate drive.

Fig. 10 is a front elevation showing the cam track profile superimposed on a suction cup flight path profile. The reference numerals are the same as in previous figures .

Fig. 11 is a schematic plan view of the flight path of a suction device of a conventional sun and planetary gear rotary feeder in which there is only one motor and a stationary sun gear. The flight path has three nodes E, F and G and these are quite sharp as there is a violent change in direction at each node. The rotary transfer mechanism according to the Fig. 1 embodiment can achieve this flight path, but it is more advantageous to control the various drives to give a profile like that shown in Figs 9 and 10 or 12 or 13. A remarkable feature of the present embodiment is that appropriate control of the various drives which are independent of each other enables different flight paths to be produced. Further variation of the flight paths is possible by changing the cam track profile if necessary, but substantial variation is possible by control of the individual drives alone.

It can be seen in Fig 12 that the suction device approaches the object holder in a linear motion (e.g. substantially perpendicular to the, usually flat, object to be picked up) from points H to A in the cycle. This helps to create a better seal and reduces wear of the suction device, compared to a situation where the suction device rolls into the objects (e.g. cartons) when picking them up from the object holder. In Fig 12 the suction device moves away from object holder in a linear motion (e.g. substantially perpendicular to objects held in the holder) from points A to I after picking up an object from the object holder. This is better than the suction device rolling immediately after picking up an object from the object holder, because such rolling can cause the object to rotate into any remaining objects in the object holder and consequently to bend and buckle or damage the object being carried by the suction device. Furthermore, if the object is a carton, moving away in a linear path should reduce the possibility that the carton will resonate just after being extracted from the object holder, making it more difficult to erect against the flight lug.

It is often the case that a rotary feeder is required to transfer an object to a receiving station on a (moving) conveyer. In this case the receiving station moves and therefore it is preferable for the suction device to move along with the conveyer in the same direction as the conveyer for a portion of its flight path during which it deposits the object on the conveyer. Thus in Figs 12 and 13 the suction device moves along with the receiving station on the conveyer (in the same direction as the conveyer) from points J to K which corresponds to node B in Fig 9. In this part of the flight path the object is deposited on the receiving station and if it is a carton it is erected by contact with a wall of the receiving station. In Fig 13 the suction device travels along with the conveyer for longer before moving away. Moving along with the conveyer is better than the suction device travelling quickly towards and then quickly away from the receiving station in Fig 11 as the smoother path means that the suction device is less prone to wear through use. Where the suction device is a suction cup alternately placed in communication with a vacuum and the atmosphere, travelling along with the conveyer means that the on/off control of the vacuum does not have to be as precise as in the Fig 11 path.

When the object is a carton it is usually erected against a side wall of the receiving station (e.g. a lug extending across a conveyer) . There is an optimum angle at which the carton should contact the sidewall (thought to be 15 to 20 degrees between the carton in its flat un- erected state and the sidewall of the receiving station) . However for a given path profile the actual angle of attack will vary depending on the size of the carton. Therefore it is preferable that the speed of rotation of the feeder arm is varied according to the size of the carton so that the desired angle of attack is achieved. For example, while it is necessary for the feeder arm to complete a given (integer) number of revolutions for every cycle of the carrier it is possible for the speed of its rotation to be varied around the cycle so that it can be speeded up or slowed down over a particular range so that the suction device has a desired angle relative to the receiving station side wall at a particular point in the cycle. Use of independent drives coupled to respective servo-motors makes this variation in speed around the cycle possible.

Fig 15 is a graph showing how the first drive 17 can be controlled (via the first servo-motor) for a portion of the path from the suction device approaching the receiving station to depositing and erecting of the carton at the receiving station to give the desired angle of attack for erecting the carton. The x-axis represents time and the y-axis represents the distance moved, each as a percentage of the total time or distance to be moved within this portion (from approach to erection of the carton, corresponding to B to J in Figs. 12 and 13) of the flight path cycle.

Line 400 represents the situation where a normal

(non-servo) motor is used or where the servo-motor is kept at constant speed. In this case the first drive moves at a constant speed through this part of the cycle. However, this will not give the best possible angle of attack for erecting the carton.

The best angle of attack is thought to be 15 to 20 degrees between the carton in its flat un-erected state and the sidewall of the receiving station as mentioned above. For a carton having a height of 120mm in its erected state then varying the speed of the first drive according to line 410 will give the desired angle of attack. Compared to line 400 the first drive starts off slower and speeds up nearer the end of this portion of the cycle. If the carton is smaller in height then the control of the drive will have to be varied accordingly to get the best angle of attack. For a carton having a height of 20mm in its erected state, controlling the first drive according to line 420 will give the best angle of attack. It can be seen that this entails having an even slower speed of the first drive at the beginning and making it even faster towards the end of this portion of the cycle. For heights in between 20 and 120mm the line would lie between lines 420 and 410 in the area marked "REQUIRED PROFILES" in the graph of Fig 15. In summary by varying the speed of the first drive between the pick up and erection of the carton an optimum angle of attack (15 to 20 degrees) for erecting the carton can be achieved for a plurality of different carton sizes. This is given by way of example only and will be appreciated by the skilled man, the rotary feeder could be controlled to give a different angle of attack or to cope with cartons taller or smaller than those described above. It is preferable that after depositing the object at the receiving station the feeder arm rotates relative to the carrier in such a way as to direct the suction device away from the receiving station. This helps to keep suction device performing a return path (in the uncritical' range) from interfering with an object carried by an adjacent suction device in the critical range (e.g. incoming to the receiving station) . If the feeder arm continued rotating in the same direction as it was prior to depositing the object then it would most likely point towards the incoming suction device and might interfere with an object carried by the incoming suction device. The cam track 80 in Fig 10 is represented by positions of the cam track follower as shown by the small circles. Each cam track follower position corresponds to a suction device 32 position. In Fig 10 for a portion 430 of the cycle where the suction device is approaching the receiving station 300 and a portion 440 of the cycle where the suction device is moving away from the receiving station, nominal lines are provided linking the cam follower positions to the corresponding suction device positions. Thus it can be seen that at portion 430 where the suction device is approaching the receiving station the suction cups are directed inwardly towards the receiving station 300, but for portion 440 of the cycle the feeder arm rotates so that the suction cups point away from the incoming suction cups and gradually start to point away from the receiving station 300. This is in contrast to conventional rotary feeders in which the feeder arm starts to rotate back after depositing the objects such that the suction device points back towards the incoming suction device which can cause interference. As will be understood from the above the suction device 32 carries an object (e.g. a carton) between the object holder 200 and the receiving station 300. However, to keep the diagrams clear and to avoid obscuring adjacent suction cup positions the object 90 is not shown in Fig 10 and is only shown for one of the suction cup 32 positions in Fig 9, although it would be present between nodes A and B.

Fig 14 is a schematic diagram showing a rotary

•transfer mechanism having a carrier, drives, feeder arms and the other features of the embodiment described above and a controller which may be part of the rotary transfer mechanism or may be provided separately. There are first, second and third servo-motors 510, 520 and 530 which are coupled to the first, second and third drives 17, 47 and 57 respectively. The servo-motors are controlled by controller 500 which has a processor that is connected to or comprises a memory 540 which may contain one or more programs for controlling the servo-motors and a user interface 550 which a user can use to select a program, modify the programs or to input parameters (e.g. carton size) used by the programs to determine the control of the servo-motors. There controller may also comprise a vacuum system control part 560 for controlling the vacuum pump 570 and/or valves for putting the suction devices in communication with the atmosphere or a vacuum produced by the vacuum pump 570.

The controller 500 controls the rotary transfer mechanism 1 by controlling the speed and direction of rotation of the servo-motors 510 to 530. The user interface 550 preferably has a display for communicating flight path or program information to the user.

The above embodiment has been described by way of example only and variations will be possible while still keeping within the scope of the invention. For instance the number of feeder arms and drives could be varied

(e.g. only two drives and one feeder arm, or three drives and two feeder arms, or three drives each coupled to a pair of feeder arms etc) and various types of sun and planetary gear system could be used (e.g. a system in which the feeder arm is coupled directly to a planetary gear rather than via an outer gear, or a system in which the planetary and sun gears are coupled by a chain and track arrangement rather than by meshing gear teeth) . Other variations will be apparent to a person skilled in the art .

Claims

1. A rotary transfer mechanism for transferring objects from an object holder to a receiving station, comprising: a first drive shaft rotably mounted on a support, a carrier rotatable with said first drive shaft, a first drive coupled to said first drive shaft for rotating the carrier relative to said support; at least one feeder arm attached to and extending outwardly from said carrier so that the feeder arm is arranged to orbit said first drive shaft when the carrier is rotated; said feeder arm being rotatable relative to the carrier and having at least one suction device for releasably engaging an object to be transferred; and a second drive for driving rotation of said at least one feeder arm, said second drive being coupled to said at least one feeder arm and independent of said first drive .

2. A rotary transfer mechanism according to claim 1 wherein the first and second drives are servo-motors or coupled to respective servo-motors.

3. A rotary transfer mechanism according to any one of the above claims wherein the at least one feeder arm is coupled to the second drive by a planetary gear system.

4. A rotary transfer mechanism according to any one of the above claims further comprising a third drive which is independent of said first and second drives, and one or more further feeder arms which are coupled to said third drive but not said second drive.

5. A rotary transfer mechanism according to any one of the above claims wherein there are a plurality of drive shafts, each drive being coupled to a respective drive shaft, the drive shafts forming a system of concentric shafts arranged such that the drive shafts are coaxial but able to rotate independently of each other.

6. A rotary transfer mechanism according to any one of the above claims wherein the feeder arm or arms are attached to the carrier by one or more respective crank members which are pivotably mounted to the carrier.

7. A rotary transfer mechanism according to claim 6 having a cam track and wherein each crank member is coupled with a respective cam follower engageable with the cam track for controlling rotation of each feeder arm relative to the carrier when in use the carrier rotates.

8. A rotary transfer mechanism according to any one of the above claims wherein the second drive means is coupled to more than one feeder arm.

9. A rotary transfer mechanism according to any one of the above claims further comprising a controller having a plurality of different programs each for controlling said at least one feeder arm to perform a different path around the drive shaft when in use the carrier is rotated by the first drive.

10. A rotary transfer mechanism according to any one of the above claims having a controller configured to control the speeds of rotation of the first and second drives and to vary said speeds between different points in their respective rotation cycles depending on the size of the object which is to be transferred.

11. The combination of a rotary transfer mechanism according to any one of the above claims together with an object holder and a receiving station; the rotary transfer mechanism having a controller configured to control the flight path(s) of the suction device (s) around the first drive shaft.

12. The combination of claim 11 wherein a plurality of feeder arms are coupled to said second drive and said feeder arms coupled to the second drive are spaced apart from each other by an amount equal to or greater than the angle subtended by the object holder and the receiving station on the axis of the first drive shaft.

13. The combination according to claim 11 or 12 wherein the controller is configured to control a vacuum system of the rotary transfer mechanism such that the suction device on the feeder arm is placed in communication with a vacuum from at least the point of the flight path where the suction device is adjacent the object holder to the point of the flight path where said suction device is adjacent the receiving station and such that the suction device is released from the vacuum at the point of the flight path where it moves away from said receiving station .

14. The combination of any one of claims 11 to 13 wherein the controller is configured to control the suction device of the feeder arm to approach the object holder in a linear motion in an approaching part of its flight path.

15. The combination of any one of claims 11 to 14 wherein the controller is configured to control the suction device of the feeder arm to move away from the object holder in a linear motion immediately after it has picked up an object from the object holder.

16. The combination of any one of claims 11 to 15 wherein the receiving station is on a conveyor and the controller is configured to control the suction device of the feeder arm to move along with the conveyor for a portion of its flight path in which it deposits an object on the conveyor .

17. The combination of any one of claims 11 to 16 wherein the controller is configured to control the speed of the first and/or second drives such that when erecting a carton held by said suction device, the angle of attack at which said carton contacts the sidewall of the receiving station, is between 15 and 20 degrees.

18. The combination of any one of claims 11 to 17 wherein the controller is configured to control said at least one feeder arm to rotate in a first direction just prior to depositing an object at the receiving station and to rotate in a second direction opposite the first direction just after depositing said object.

19. A method of transferring an object from an object holder to a receiving station using a rotary transfer apparatus according to any one of claims 1 to 10.

20. A method according to claim 19 wherein a vacuum system of the rotary transfer mechanism is controlled such that the suction device on the feeder arm is placed in communication with a vacuum from at least the point of its flight path where the suction device is adjacent the object holder to the point of its flight path where said suction device is adjacent the receiving station, and the suction device is released from the vacuum at the point of its flight path where it moves away from said receiving station.

21. A method according to claim 19 wherein the suction device of the feeder arm is controlled to approach the object holder in a linear motion.

22. A method according to claim 19 wherein the suction device of the feeder arm is controlled to move away from the object holder in a linear motion immediately after it has picked up an object from the object holder.

23. A method according to claim 19 wherein the receiving station is on a conveyor and the suction device of the feeder arm is controlled to move along with the conveyor for a portion of its flight path in which it deposits an object on the conveyor.

24. A method according to claim 19 wherein the second drive is controlled such that during erecting of a carton at the receiving station, the angle of attack at which said carton held by the suction device contacts the sidewall of the receiving station is between 15 and 20 degrees .

25. A method according to claim 19 wherein said at least one feeder arm is controlled to rotate in a first direction just prior to depositing an object at the receiving station and to rotate in a second direction opposite the first direction just after depositing said object at the receiving station.