Conventionally endless conveyor belts are driven by friction with the belt extending around more or less large diameter drive pulleys or rollers through which drive is transmitted to the belt. It will of course be appreciated that this requires the belt to have a relatively strong construction in order to be able to transmit the required driving forces along the very long belt runs often required and thus such belts often require the inclusion of special tensile force-sustaining members such assteel cables along their length. This in turn leads to relatively high manufacturing costs on the one hand and on the other hand to considerable problems of belt repair if the belt breaks.

It has also previously been proposed to provide conventional flat or troughed conveyors belts with electromagnetically conductive elements embedded therein below the material carrying surface for use in a linear motor drive arrangement for the conveyor belt. To date though there does not appear to have been any significant exploitation of such proposals due to various practical problems such as the low electrical efficiency resulting from the linear motor stator elements being disposed facing the 'clean' underside of the belt. Another major drawback of such belts is that they can only travel in straight lines. There have also previously been proposed (e.g. in O87/03565) so-called 'bag ⁷ conveyors wherein opposite side edges of the belt are brought into sealing interengage ent with each other and the belt and its load suspended from the interengaged side edges which contain special tensile force-sustaining members such as steel

cables along their length. Whilst such arrangements allow the belt to negotiate relatively small radius carves, the abovementioned problems of high manufacturing cost, belt breakage etc. remain.

It is an object of the present invention to avoid or minimise one or more of the above disadvantages.

The present invention provides an endless belt conveyor having at least one endless belt having a load supporting portion, and a generally longitudinally extending flexible rail rotor means projecting at least along a driving section of the belt run and generally outboard of said load supporting belt portion and remote from a load carrying surface of said load supporting portion, said conveyor being provided with belt support and guide means, and linear motor stator means, said rail rotor means being formed and arranged for interaction with said linear motor stator means disposed alongside said rail rotor means in use of the conveyor, so as to impart drive to said rail rotor means and thereby to said belt.

The rail rotor means may be comprised by a longitudinally extending side edge portion of the belt outboard of a central load supporting portion, or, generally longitudinally extending rib or fin structure projecting outwardly of the reverse or underside surface of the belt remote from the load carrying surface of the belt, conveniently at the central load supporting portion of the belt. With such configurations, the rail rotor can be maintained in a substantially clean condition without the need for special cleaning thereof, and stator means which extend substantially around the rail rotor means may be used thereby maximising electrical and/or magnetic coupling or interaction between the rotor and stator means thereby in turn maximising the efficiency of the motor drive. Various forms of conveyor belt may be used in the

conveyor of the invention including both troughed belt conveyors and so-called bag conveyors wherein the belt has sealing engagement portions at opposite sides which are held together in sealing interengagement along at least part of the conveying path.

It will also be appreciated that various types of linear motor may be used in the conveyors of the invention with different forms of flexible rail rotor and linear motor stator means, or combinations thereof. Thus there may be used an induction type linear motor wherein the flexible rail rotor means is in the form of a continuous electrical conductor e.g. copper or aluminium strip or web or a plurality of transversely disposed electrical conductor loop elements closely and regularly spaced along the length of the flexible rail rotor means. This type of motor, also known as an asynchronous motor, has particularly good initial torque and is thus preferred where the conveyor operation involves frequent starting and stopping. It may also be advantageously incorporated in other conveyor systems for assisting starting of the conveyor belt which is subsequently driven by another type of linear motor.

Synchronous linear motors generally have a flexible rail rotor with a plurality of regularly spaced magnetic pole means, which may be permanent or electromagnetic in nature, with a pole pitch corresponding to that generated within the stator unit(s), the stator means being formed and arranged so that when excited by a suitable electric current, a periodic magnetic field (travelling longitudinally along the rail rotor) is generated therein for interaction with the rail rotor magnetic poles.

Another type of linear motor that may be used is a stepper (or reluctance) type motor wherein the flexible

rail rotor has a plurality of regularly spaced magnetic material (e.g. iron) pole means at a fixed pitch different from that of magnetic poles generated in the stator unit(s). More particularly the stator units are generally formed and arranged so that an electric current is applied thereto for alternating generation of a plurality of magnetic pole sets offset longitudinally along the rail rotor, which interact sequentially with the rail rotor poles.

Thus in a further aspect the present invention provides an. ^" , endless belt suitable for use in an endless belt conveyor of the invention which belt has two longitudinal edge portions at opposite sides outboard of a central, load supporting, portion, with a generally longitudinally extending flexible rib or fin structure projecting outwardly of the reverse or underside surface of the belt remote from a load carrying surface of the belt and incorporating a flexible rail rotor means, said rail rotor means being formed and arranged for interaction, in use, with a linear motor stator means in use of the conveyor so as to impart drive to said rail rotor means and thereby to said belt.

In another aspect the present invention provides an endless conveyor belt suitable for use in an endless belt conveyor and having two longitudinal edge portions at opposite sides of the belt with longitudinally extending sealing engagement portions disposable in sealing engagement with each other, in use of the conveyor along at least part of a material conveying pathway, so as to define a generally tubular material conveying compartment, by means of guide roller means formed and arranged for holding said sealing engagement portions of the belt in sealing engagement with each other along at least part of a material conveying pathway of said belt, at least one of

said side edge portions having a generally longitudinally extending flexible rail rotor means disposed generally outboard of the sealing engagement portion therein, for interaction, in use of the belt, with linear motor stator means, so as to impart drive to said rail rotor means and thereby to said belt.

In another aspect the present invention provides an endless belt conveyor having at least one endless belt with two longitudinal edge portions at opposite sides of the belt outboard of a central, load supporting, portion, at least one of said side edge portions having a generally longitudinally extending flexible rail rotor means, said conveyor being provided with belt support and guide means, and linear motor stator means, said rail rotor means being formed and arranged for interaction with said linear motor stator means disposed alongside said rail rotor means in use of the conveyor, so as to impart drive to said rail rotor means and thereby to said belt.

In a further aspect the invention provides an endless belt conveyor having at least one endless belt with two longitudinal edge portions at opposite sides of the belt with longitudinally extending sealing engagement portions disposable in sealing engagement with each other, in use of the conveyor along at least part of a material conveying pathway, so as to define a generally tubular material conveying compartment, at least one of said side edge portions having a generally longitudinally extending flexible rail rotor means disposed generally outboard of the sealing engagement portion therein, said conveyor being provided with guide roller means formed and arranged for holding said sealing engagement portions of the belt in sealing engagement with each other along at least part of a material conveying pathway of said belt, said conveyor also being provided with linear motor stator

means, said rail rotor means being formed and arranged for interaction with said linear motor stator means disposed alongside said rail rotor means in use of the conveyor, so as to impart drive to said rail rotor means and thereby to said belt.

Preferably the belt is supported by said support and guide means so that said at least one side edge portion . of-, said rail rotor means extends generally vertically, whereby optimum relative disposition of the rail rotor means and linear motor stator means is facilitated and/or said stator means can be formed and arranged so as to extend around opposite sides of said rail rotor means.

If desired there may be provided a large plurality of linear motor stator means disposed along said conveyor and formed and arranged for also supporting said rail rotor means and thereby said belt. Advantageously though there are provided guide and support roller means for guiding and supporting said belt whereby stators are only required for longitudinal driving and may be widely spaced e.g. at 100 to 500m intervals.

Thus with an endless belt conveyor of the invention it is possible to provide relatively efficient linear motor driving of the belt with the various usual advantages of linear motor drives including minimal friction and no rotating parts with consequentially increased reliability, high speed driving and ease of control including both acceleration and deceleration. In addition by disposing a plurality of linear motor stators along the material conveying run section(s) of the conveyor belt pathway the maximum belt driving force can be applied directly where it is most needed thereby minimising the need for the transmission of large driving forces through the whole length of the belt from a remote return drive pulley at

one end of the conveyor belt installation thereby in turn allowing the use of lighter belt constructions without the need for special tensile force sustaining members such as steel cables. The risk of belt breakage is also significantly reduced and even where belt repair is required this will generally be significantly simplified. Moreover by bringing together the belt edge portions, the conveyor belt may readily negotiate curves and bends of relatively limited radius and the material being conveyed is substantially contained thereby avoiding spillage resulting in loss of material and/or damage to the conveyor resulting from such spillage.

Preferably at least one of the belt edge portions is formed and arranged with shoulder means for engagement with roller means mounted in a rolling axis, the roller means having a substantial horizontal component for substantially supporting the weight of the belt and its contents. Advantageously a plurality of roller means is provided at opposite sides of the belt and formed and arranged for holding the belt edge portions together in sealing engagement.

Particular forms of flexible rail rotor means that may be used in accordance with the present invention include both continuous and discontinuous segmented electromagnetic conductors of various forms and regularly spaced magnetic elements with magnetic poles of opposite polarity alternating along the length of the flexible rail rotor, according to the type of linear motor used as discussed hereinabove and the degree of flexibility required in the rail e.g. depending on the radius of curvature of the bends required to be negotiated by the belt and whether the rail is required to negotiate horizontal and/or vertical plane bends. Thus, for example, there may be used a continuous flexible conductor

strip of suitable metal or alloy e.g. copper plated steel, hard brass, or aluminium alloy in a linear induction type motor; or a segmented generally channel-form rail formed of more or less closely spaced sections crimped around the free outermost edge of the main body of the rubber or like flexible non-conducting material belt in a tubular type construction linear motor. A similar segmented construction with magnetic material ( e.g. iron or steel) or magnetised material could form the bases of a stepper, reluctance or synchronous linear motor.

Particular suitable linear drive motor stator means that may be used in conveyors of the invention include generally 'U' or 'C - shaped section stator means disposed so that a substantial part of the rail rotor means section projects into or is disposed within said 'U' or 'C - shaped section, so as to maximise the efficiency of the electromagnetic coupling between the stator and rotor means of the motor. Again the nature of the stator will depend on the type of linear motor being used as well as the particular form of rail rotor employed and/or the form of electric power input used.

It will also be appreciated that more complex rotors and different types of stator means may be employed in conveyors of the invention, for example, where it is required to use one type of motor e.g. an induction motor for starting the conveyor and another type e.g. a synchronous type for maintaining running of the conveyor.

Further preferred features and advantages of the invention will appear from the following detailed description given by way of example of some preferred embodiments illustrated with reference to the accompanying drawings in which:

Fig. 1 is a sectional elevation through the principal parts of a first belt conveyor of the invention;

Fig. 2 is a sectional elevation of a second belt conveyor of the invention; Fig. 3 is a detail plan view of the belt of Fig. 2 showing the flexible rail thereof;

Fig. 4 is a partial sectional elevation of the third embodiment;

Fig. 5 is a schematic illustration of the magnetic field and current loop arrangement in the above described embodiment of Fig. 4;

Figs. 7 and 8 are detail sectional elevations of further embodiments;

Fig. 9 is a schematic plan view of a belt conveyor installation of the invention;

Fig. 10 is a schematic sectional view of the installation of Fig. 9 in the plan X-X;

Figs.11 and 12 are generally similar views of further installations; Fig. 13 is a schematic sectional elevation of the installation of Fig.12 in the plane XIII-XIII;

Fig.14 is a detail perspective view of a different form of rail rotor for a synchronous linear motor drive system; Fig. 15 is a vertical transverse section through another form of 'bag' conveyor of the invention;and

Fig. 16 is a sectional perspective view of a third embodiment of the invention.

Fig. 1 shows an endless belt conveyor 1 comprising an endless belt 2 of rubber or like material with two enlarged section longitudinal edge portions 3, 4 along opposite longitudinal sides 5 of the belt 2. The enlarged section side edges 3, 4 are shaped and configured in generally known manner (see for example international patent publication no. WO 87/03565) and are brought together in sealing interengagement along part of a conveying path in which they run between closely spaced

vertical axis guide rollers 6, and over an inclined axis support roller 7 (shown in chain line) . Side edge portion 4 is located above side edge portion 3 and has projecting upwardly therefrom and along its entire length a flexible metal conductor strip 8 forming a rail rotor which runs between the arms 9 of a linear drive motor stator 10 in closely spaced relation thereto with a small air gap 11 between each side 12 of the flexible "rail" element 8 and a respective arm 9 of the stator 10. The stator 10 is energised in order to cause linear motion of the rail element 8.

As may be seen in Fig. 1 the central portion 13 of the belt 2 defines a generally tubular bag in which bulk material 14 is securely contained and transported. Figs. 2 and 3 show a generally similar conveyor 1 which has a slightly different belt edge section 15, 16 formed and arranged so that the belt 2 may be supported and the edges held together in sealing engagement by oppositely inclined guide and support rollers 17 at each side of the belt 2. The rollers 17 are rotatably mounted 18 on support members 19 depending from a conveyor support gantry 20. In this case, one side edge 16 has a vertically upwardly projecting web 21 in which are embedded ferromagnetic metal cables 22 extending longitudinally of the belt 2. In addition a plurality of generally ^, U' shaped section aluminium or copper segments 23 are crimped on to the rubber web 22 at closely spaced intervals 24 there-along. The segments 23 are secured in place by aluminium rivets 25 which extend through the distal ends 26 of the segments 23 and the web 21 disposed therebetween. The rivets 25 also complete a closed loop electrical circuit through the segments 23. With this particular form of segmented "rail" it will be appreciated that a greater degree of flexibility may be provided in the belt than in the embodiment of Fig. 1, thereby facilitating routeing of the

conveyor belt around bends in both horizontal and vertical planes.

Fig.4 shows another embodiment in which the belt side edges 3, 4 are configured for sealing interengagement and guide roller support in generally similar manner to that in the embodiment of Fig. 1. In this case though side edge 4 has a web 21 generally similar to that in the embodiment of Fig.2 but with a reinforcing fabric strip 27 extending therealong which helps carry the weight of the belt 2 and bulk material 14 therein in between successive support rollers. Aluminium segments 23 are secured to the web 21 in generally similar manner to that shown in the embodiment of Fig. 2 using aluminium rivets 25, but with a pair of steel strips 28, extending along the length of the belt, sandwiched between the aluminium segments 23 and opposite sides 29 of the web 2i. The steel strips 28 are separated by a small air gap 30 opposite the free edge 31 of the web 21 so as to separate their magnetic fields as described below with reference to Fig. 5. The linear drive motor stator 10 is not shown in Fig. 4 in the interests of clarity.

Fig. 5 shows, generally schematically, the interaction between an induced electric current loop 32 in the rail segments 23 shown in solid outline and magnetic fields 33 shown in dashed outline extending through and around the stator 10 for the embodiment of Fig. 4.

Figs. 7 and 8 show further alternative forms of side edge configuration. In the case of Fig. 8 it may be noted that each side edge 35, 36 contains a longitudinally extending conductor strip 37.

Fig. 9 shows a conveyor installation in which the delivery and return sides 38, 39 are disposed vertically

above each other (see Fig.10) over the main part of belt pathway. At one end, the belt 2 is routed around a vertical axis return drum 38 and at its other end, around a horizontal axis return drum 39. The belt is guided along with the edges 3, 4 held together in sealing engagement throughout the major part of the belt pathway except at a loading station 40 where the edges are separated sufficiently to allow bulk material to be fed in 41 to the interior of the belt. The belt 2 is also opened out into a substantially flattened form where it passes over the horizontal axis return drum 39 for discharge of the bulk material 42.

Fig.11 shows a generally similar arrangement but in this case both return drums 38, 43 are of vertical axis disposition and in addition the belt is routed around two further vertical axis drums 44 at positions where the belt pathway is required to change substantially its direction in the horizontal plane. In this case both loading and discharge stations 41, 45 have the belt only partly opened out. The installation of Fig.12 is generally similar to that of Fig. 11 except that in this case the delivery and return sides 46, 47 of the conveyor belt pathway are disposed in side by side disposition (see also Fig.13).

It will be appreciated from the above described examples wherein a substantially vertical 'flexible rail' projects upwardly of the main body of the belt, these will have a further advantage in that the necessary small air gap between the 'rail' and the linear drive motor stators may be readily maintained to the necessary degree of precision since this part of the belt is substantially free of any loading in the, horizontal, direction across the air gap. Also insofar as the weight of the belt and bulk material carried therein is generally supported by the rollers, (and inbetween by the belt itself) the linear

drive motor is required only to provide drive in the direction of the belt pathway, without the need for also supporting the weight of the belt and bulk material therein and maintaining a vertical air gap between the rotor and stator means.

As explained hereinbefore other forms of linear motor drive may also be used. Fig. 14 shows part of a flexible rail rotor for use in a synchronous linear motor, wherein the belt side edge portion 3 has an upwardly projecting web 21 in which is disposed a series of regularly spaced permanent magnetic elements 48 with poles of alternating polarity along the 'flexible rail'.

Fig. 15 shows another form of 'bag' conveyor of a type generally similar to that disclosed in W089/01451. In this case the conveyor belt 2 is provided with a central longitudinally extending rib 49 along its underside 50. An electrically conducting metal fin rail rotor 8 projects vertically downwardly from the rib 49 to run between the arms 9 of a stator 10, the rib 49 being supported on rollers 7 which carry the weight of the belt 2 and bulk material load 14. Upper side edge portions 51 of the belt 2 are laterally supported against guide rollers 52 either side of the conveyor belt. Thus in this case also the linear motor drive is used only to drive the belt longitudinally and does not support the belt and its load.

Fig. 16 shows another preferred embodiment of the invention in the form of a suspended cylinder belt conveyor system of a type generally similar to that disclosed in U.S. patent 4,850,476. In this case the edge portions 3, 4 of the belt 2 are kept together by clamp arrangements 52 generally similar to that disclosed in the abovementioned patent, said clamps 52 clamping the belt 2 at regular intervals e.g. 2-3 metres along the required

sealed portion of the belt run. Incorporated in the clamp arrangements 52 are reaction plates 54, which when said clamps 52 are clamped in position the conveyor belt 2 and said clamps 52 combine to form rail rotor means 8. The clamp arrangements 52 are formed and arranged to travel along a monorail 56 on rollers 58. Stator means 10 are placed around the monorail 56 at regular intervals e.g. 50-100 metres along the monorail 56 travel path whereby said rail means 8 and said stator means 10 combine to drive said 'bag' conveyor 2.

At loading and unloading stations along the length of the belt run, switch mechanisms (not shown in the interests of clarity) , are activated by the passing roller 58 causing the clamping arrangement 52 to open as required. The clamping arrangements 52 continue along the monorail 56, whilst the belt 2 is supported in an open condition by horizontal support rollers. When the belt 2 is required to be closed and clamped, inclined rollers bring the belt 2 edge portions 3, 4 together in close proximity to the underside of the monorail wherein a clamping arrangement 52, activated by switching mechanisms, closes and clamps the belt 2 edge portions 3, 4. The flexible rail rotor means 8 electromagnetically coupling with said stator means 10 to drive said belt 2.