BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates in general to the field of conveyor systems. More particularly, the present invention relates to systems having direct current (DC) brushless motorized pulleys.

2. Discussion of the Related Art Within this application several publications are referenced. The disclosures of all of these referenced publications in their entireties are hereby expressly incorporated by reference into the present application for the purposes of indicating the background of the present invention and illustrating the state of the art.

Motorized conveyor pulleys have been used for several decades. For example, motorized pulleys are used to drive the belt or chains in conveyor systems and take the place of a separate drive motor, reduction gear box sheaves and drive belts or sprockets and chains. Motorized

pulleys are usually used at the head of a conveyor and generally offer an electric drive motor and reduction gearing encased within the outer drum of the conveyor pulley.

Most manufacturers now build alternating current (AC) motor, fixed gear set, motorized conveyor pulleys. Within a particular drum size, there are often several horsepower choices and then several speed/torque (often termed"belt pull") combinations within each horsepower. For example, one conventional AC motor design using the 5.45" diameter drum, has 5 horsepower selections and 26 speed choices within those horsepower ranges for a total of 130 combinations.

Nevertheless, by using an inverter, one can offer variable speed to an AC motor, and some manufacturers do offer 2 speed units.

There are several problems with AC motorized drives. One is that as the revolutions per minute (RPMs) are reduced, there is a sharp reduction in torque, often rendering the drive pulley incapable of turning the belt. Therefore, AC motor remain primarily of a single speed design with speeds changed by gearing. These design limitations require the users to make many permanent choices with little flexibility for change if the unit is installed and the speed or torque is found to be deficient. From a manufacturing standpoint, the many choices reduce economies of scale and add to lead times since units cannot be pre-built. From a distribution standpoint, the varied choices of AC motors require a highly trained sales force which limits the ability to train and bring on line wide channels of distributors and sales agents. Another problem is that AC drives run very hot making them impractical and dangerous for some applications.

The actual selection of belt speed in prior art pulley at the user level is often imprecise.

For example, speeds can vary according to material, moisture content, grain size, etc. Thus, many users prefer to use standard drive systems and change the ratio of inexpensive sprockets or sheaves to achieve or change to a desired speed rather than buy a far more expensive motorized pulley and risk purchasing a device which is the wrong speed for their application and cannot be

corrected economically. Some inventors have offered solutions to the problems associated with using prior art motorized conveyors.

The below-referenced U. S. patents disclose embodiments that were at least in-part satisfactory for the purposes for which they were intended. The disclosures of all the below- referenced prior United States patents in their entireties are hereby expressly incorporated by reference into the present application for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art.

United States Patent 4,365,187 discloses a brushless direct current motor with a permanent magnet rotor which employs a Hall switch to effect commutation.

United States Patent 5,088,596 discloses a motorized conveyor roller in which the motor and drive gear is contained inside the roller. The conveyor roller is hollow and contains a motor which drives a drive member through a gear reducer assembly. The periphery of the drive member is frictionally connected to the conveyor roller. A preferred embodiment disclosed in this patent uses a conventional brush commutation DC motor. However, the use of rare earth magnets on the rotor of the DC motor is not disclosed in this patent.

United States Patent 5,145,169 discloses a conveyor pulley having a motor contained therein where a rotor rotates about a stator in order to drive the cylinder body. A variable reluctance-type stepping motor is disclosed in the preferred embodiment.

United States Patent 4,987,333 discloses a flat type brushless motor and pulley assembly which includes a flat stator having a cutout section formed therein. The stator works with a flat rotor which has multiple permanent magnets for rotating a pulley member.

United States Patent 5,228,558 discloses an accumulating conveyor which includes a drive roller having a DC motor and a gear assembly. _ United States Patent 5,086,904 discloses a"parts supply arrangement"which involves two separate and interchangeable stationary portions of a brushless DC linear motor, and a carrier device on which parts are placed for transportation by attaching them to the moveable portion of the motor. By providing two stationary portions of the motor, the parts supplying system disclosed in this patent is capable of automatically supplying parts to part mounting machines.

While the use of a brushless DC motor within a conveyor is contemplated in the prior art, the use of a solid state Hall effect device to advance the field in a motor winding of a brushless DC motor within a drum-type conveyor pulley assembly on a variable speed conveyor is not.

Further, the use of NEO rare earth magnets in a brushless DC pulley drum motor is also not disclosed. A DC motor and pulley drum with a continuous through shaft is also not disclosed.

Other novel features will be outlined below.

SUMMARY AND OBJECTS OF THE INVENTION The present invention has an infinitely variable speed design that matches the maximum horsepower and torque values for generally any offering within a drum size, giving it a"one size fits all"approach for optimum marketing and mass distribution needs. The speed of the pulley drum is selected by the user using the controller. Maximum torque remains constant at any speed setting assuring adequate conveyor belt pull. One purpose of the DC brushless motorized conveyor pulley is to offer an infinitely variable speed conveyor system, running at constant high torque levels that confronts the user with less choices, makes the training of sales personnel easier and therefore opens markets through a broad distribution network and makes the use of such a device more attractive to users who have avoided installing motorized pulleys in the past.

A primary object of the invention is to provide a brushless DC motorized drum conveyor pulley that has infinitely variable speeds, has a soft start, stop, and restarts and is reversible.

Another object of the invention is to provide an apparatus that is ruggedized and reliable, thereby decreasing down time and operating costs. Another object of the invention is to provide an apparatus that has one or more of the characteristics discussed above, but which is relatively simple to manufacture, assemble using a minimum of equipment, and use.

Another object of the invention is to provide an apparatus that has one or more of the characteristics discussed above but which is relatively simple to setup and operate using relatively low skilled workers.

Another object of the invention is to provide a motorized drum pulley that offers significantly greater control options for conveyor systems such as reversibility, dynamically changeable speed control, synchronization between a series of conveyors within a system, and the ability to pause, stop, start or incrementally advance a belt.

In accordance with a first aspect of the invention, these objects are achieved by providing an apparatus comprising a motorized conveyor pulley which utilizes a brushless, DC motor.

Specifically, rotary motion in the conveyor pulley is generated by a motor core which may comprise a series of NEO rare earth magnets or magnets of another material bonded to a fixed center shaft which rotates within the motor housing having a stationary motor winding. The field of the motor winding may be advanced or commutated by the solid state Hall effect ring which is bonded to one face of the motor winding. The brushless DC Motor may also use a mechanically rigid, continuous center through shaft.

It is yet another object to provide a conveyor that: avoids the use of brush commutation which requires periodic replacement of the brushes and turning of the split ring commutators,

offers low cost, generally infinitely variable speed using an inexpensive DC controller and speed control as the standard control, offers generally flat torque values over a wide range of RPMs making variable speed practical, generally offers higher energy efficiency than AC counterparts because of lower current draw, offers generally greater thermal efficiency and lower temperatures because a DC motor runs cooler than an AC motor and heat dissipation is accomplished more easily because the DC motor is generally smaller, and provides feedback as to armature position within the motor and RPM as a function design.

It is still another object to provide a shaft that, while segmented, mechanically acts as a center through shaft through the entire installed length of the pulley. This design virtually eliminates offset shaft and cantilevered loads as found in conventional and current designs. This in turn eliminates moment loading of bearings and gears, reduces the number of moving parts, evenly distributes loads through the device, and more fully supports even load distribution to the rotating drum via cycloidal or planetary gears.

Another object is to provide the ability to synchronize the speeds of a series of conveyors using a motorized conveyor pulley or one conveyor using several of the motorized conveyor pulleys. Another object is to provide a system that through internal feedback can maintain constant speed of the system under varying loads, provide for soft starts and stops, stop-restart, dwell, jogging and the ability to incrementally advance the pulley, and provide the conveyor with a preset incremental length. Yet another object is to provide the ability to easily control the motorized conveyor pulley with a PC, digital front end or PLC.

These, and other, aspects and objects of the present invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the present invention, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS A clear conception of the advantages and features constituting the present invention, and of the construction and operation of typical mechanisms provided with the present invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings accompanying and forming a part of this specification, wherein like reference numerals designate the same elements in the several views, and in which: FIG. 1 illustrates a generally schematic side elevational view of a conveyor system of the present invention; FIG. lA illustrates a generally schematic side elevational view of a plurality of conveyor systems according to the present invention; FIG. 2 illustrates a longitudinal section view taken through the line 2-2 of FIG. 1; FIG. 2A is an exploded view of one end of another embodiment of the present invention; FIG. 3 illustrates a section view taken through the line 3-3 of FIG. 2; FIG. 4 illustrates a section view taken through the line 4-4 of FIG. 2;.

FIG. 5 illustrates a front elevational view of one embodiment of the gearing assembly of the present invention; FIG. 6 illustrates a front elevational view of another embodiment of the gearing assembly of the present invention; and FIG. 7 is a graph showing the torque graphed as a function of speed in terms of RPMs and of amperage for the pulley motor of the present invention.

In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not

intended that the invention be limited to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the word connected or terms similar thereto are often used. They are not limited to direct connection but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art.

DESCRIPTION OF PREFERRED EMBODIMENTS 1. Resume In the motorized conveyor pulley system of the present invention, outer end plates are fixed to the pulley drum via bolts, threaded pins, welding or a press fit. Either 0-rings or a liquid sealant are used to seal this surface. A mechanically fixed assembly rotates about a fixed center through shaft assembly and is comprised of a series of mechanically joined, non-rotating elements (gear end end cap and first stationary shaft, three gear pins, motor end cap, motor housing and drive end cap and second stationary shaft). Shaft sealing, that is sealing the interior of the device against outside contamination, may be accomplished by an outer stamped metal bearing seal over a washer style plastic seal that fits over a shaft seal that is contained within a machined recess in the outer casing. Washdown duty seals and labrynith seals are also contemplated. Both stationary shafts may be clamped to the conveyor bed by means of a take-up or other device.

Rotary motion is generated by the motor core. This is comprised of a series of NEO rare earth magnets bonded and fixed to a center shaft. The motor core's rotating motion is contained by two radial bearings. Both bearings preferably press fit into two elements of the non-rotating through shaft assembly-one into the motor end cap and the other into the drive end cap and stationary shaft. The motor core is rotated by the electrical field of the motor winding. The field is advanced or commutated in the motor winding by a Hall effect device which is bonded to one

face of the motor winding. Power is brought to the motor windings via leads that are passed through the hollow center of the drive end cap and stationary shaft. These leads are terminated exterior to the open end of the stationary shaft where they can be connected to a variety of controllers. A controller may be used to regulate the speed, direction, and allow for integration into computer, PLC, or digitally based control system.

Transmission of rotational power to the drum, a reduction in the motor's speed and an increase in output torque is accomplished by a planetary or cycloidal gear set. In one embodiment a planetary gear set is provided. The sun gear is mechanically fixed to the shaft of the motor core. It causes the planet gear or gears to rotate about the gear pins fixed between the motor end cap and gear end cap and stationary shaft. The rotation of the planet gears transmits rotary motion to the output ring gear which is mechanically fixed to the interior surface of the pulley drum. In a second embodiment, a twin disk cycloidal gear arrangement is used.

2. Svstem Overview The present invention and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments described in detail in the following description.

Referring generally to the drawings FIGS 1-7, it can be seen that the present invention relates to a motorized pulley system 5, preferably a conveyor system 5, for moving an article 8 or articles which preferably includes a belt 10, a plurality of rollers 12, and a motorized pulley assembly 15 for driving the belt 10. Referring specifically to FIG. 1, the conveyor system 5 is shown where the motorized pulley assembly 15 is comprised of an outer pulley drum 18 containing a brushless DC motor 24 for providing variable speed to the pulley. The drum 18 and

the rollers 12 may be mounted to the floor of factory by a mounting post 20. The rollers 12 and the drum 18 may be secured to the posts 20 by a clamp 19 as is known in the art.

In addition, the motorized pulley system 5 of the present invention may be used in web feed rollers (such as those disclosed in U. S. Patent No. 5,657,941, incorporated herein by referenced), film feed rollers, shrink wrap systems (such as those disclosed in U. S. Patent No.

5,575,138, incorporated herein by reference), slider bed conveyors, troughing conveyors, slat conveyors, table-top conveyors, roller bed conveyors, plastic chain conveyors, and other such systems.

Most parts of the conveyor system 5 are constructed of stainless steel although some other low carbon steel or other suitable material will suffice. The conveyor system 5 may be also constructed of other suitable materials such as aluminium, steel, and plastic. The conveyor system 5 of the present invention generally provides consistent torque output over a wide range of RPMs. Further, most parts of the system 5 are lubricated with synthetic lubricators to ensure maximum lubrication protection and cleanliness.

The belt 10 may be made of rubber or some other suitable material. The belt 10 may also be constructed of multiple steel chain links. Additionally, the belt 10 may be constructed of webbing, lattice or a variety of other materials and in different configurations as is known in the art. Preferably, the belt 10 has a speed range which may be 30-300 feet per minute (FPM) which is generally equivalent to about 21-214 RPM.

As shown in Fig. 1A, preferably at least one roller 12 is in operable association with the conveyor belt 10 and driven by the motorized pulley assembly 15. Preferably the plurality of rollers 12 are spaced generally every one to three feet along the conveyor system 5. Each of the rollers 12 is preferably in operable association with the conveyor belt 10 and indirectly relies on

the motorized pulley assembly 15 for rotation. However, as is known in the art some rollers may not be associated with the belt 10 and may rotate under their own power. A pair of stationary shafts 34,50 connect to the pulley assembly 15 to conveyor belt 10. The rollers 12 have preferably a similar outer design as the pulley assembly 15 and have connecting shafts 14 as well.

The preferably cylindrical drum 18 may have a variety of configurations. For example, the drum 18 may have a crowned or straight profile. Further, the drum may have a machined or knurled outer casing or finish for added friction. The pulley drum 18 is preferably a standard 5.45" outer diameter pulley for adoption into generally any existing conveyor system. However, a variety outer diameters, such as 4.25", 8.0", and 30"are contemplated.

FIG. 1 A shows a series of conveyor systems 5 of the present invention, one of which utilizes a telescoping take-up member 22. The pulley drum 18 is mounted to the by clamp 19 which is secured to the mounting post 20 by bolts 19a (Fig. 2). The telescoping take-up 22 may be connected to the conveyor system 5 by preferably four bolts 22a as shown or other fasteners.

Referring now to FIG. 2, the motorized pulley assembly 15 has a pulley drum 18 which has a first end 28, a second end 30, and an inner cavity 32. A first outer casing end plate 26a seals off the first end 28 of the pulley drum 18. The outer casing end plate 26a has a bore 26b therethrough. A first stationary shaft 34 has a first shaft portion 34a and a second shaft portion 34b. The first stationary shaft 34 first shaft portion. 34a is received in the first outer casing bore 26b. A gear end cap 35 may be connected to the second portion 34b of the stationary shaft 34.

End plates 26a, 26c are secured to the drum 18 by a plurality of bolts 18a, 18b, respectively, or other suitable fasteners which be tightened to seal the inner cavity 32 of the drum 18 and the motor 24 from liquids or other potentially harmful contaminates. The motorized conveyor pulley

assembly may also have a magnetic particle trap (not shown) to collect particles which could otherwise damage the motor 24 and gears.

The brushless DC motor 24 may include a center shaft 31. Magnets 33 are fixed around the center shaft 31. The motor 24 also includes a motor core 39 having a hole therethrough. A motor winding 40 generally surrounds the motor core 39. The motor winding 40 may be constructed of copper or some other suitable material, as is known in the art. A motor end cap 44 has a hole 44a therein for receiving the shaft 31. A solid state Hall effect ring 27 may be bonded to one face of the motor winding 40.

A second stationary shaft 50 is received in the hole 48a of the drive end cap 48. The first and second stationary shafts 34, have a portion that sticks out of the ends 28,30 of the drum 18.

As best illustrated in Fig. 3, these first portions 34a, 34c of the shafts 34,50 may have flatten sides which help clamps 19 keep the shafts 34,50 from rotating. The motor 24 may also have a skewed stator design to minimize cogging a low RPM.

Referring again to Fig. 2, leads 82 fit into the hollow first portion 37c of the second shaft 50 connect the motor 24 to a AC power source 84 which may be a conventional outlet. The leads 82 bring power to the motor windings 40. The leads terminate exterior to the open end of the second stationary shaft 50 and connect to controller 72. No slip ring is necessary because the leads 82 run directly into the stationary shaft.

Preferably, the brushless DC motor 24 is operable within a voltage range between 100 and 250 DC volts. The DC motor 24 is preferably capable of producing at least one horsepower of torque at the pulley drum 18, although a variety of torque outputs are contemplated including a motor capable of producing 100 HP of torque. The motor 24 may also be used to incrementally advance the conveyor belt 10. The motor 24 also preferably has class"H"insulation for added

safety. The motor 24 of the conveyor system of the present invention may also be more energy efficiency than prior art motors because of low current draw. For example at 1 HP, the draw would be about 5.8 amps. This also may also increase the motor's thermal efficiency.

The magnets 33 may be rare earth magnets or magnets of another suitable material. The magnets 33 are preferably constructed from neodymium (NEO). Iron and boron are preferably combined with the NEO. Any other rare earth magnets, such as those made samarium cobalt, which possess excellent magnetic performance may be used. For example, the NEO rare earth magnets 33 provide for higher HP and torque output from the motor 24.

A gear assembly 43 is provided to transmit rotational power to the drum, reduce the motor's speed and increase output torque. In one embodiment, an output ring gear 36 of the gear assembly 36a may be adjacent to the gear end cap 35. In this embodiment, at least one planet gear 37 is operably associated with the output ring gear 36. A sun gear 38 is connected to the center shaft 31 of the motor 24. The sun gear 38 may be in operable communication with one or more planet gears 37,37a, 37b, as shown in FIG. 5, to drive the planet gears. The gears act to evenly distribute radial load and motion to an inner diameter of a rotating drum. The gears may rotate about gear pins fixed between the motor end cap and the gear end cap and stationary shaft.

The planet gears transmit rotary motion to an output ring gear which is mechanically fixed to the interior surface of the pulley drum. Additionally, the gear assembly 43 may consist of a compound planetary gear assembly which may include spur gears, helical gears, and planetary gears.

Referring now to Fig. 2, the motor 24 rotates on a first motor bearing 42 having a hole therethrough in communication with the second shaft portion 34d at the drive end cap 48. The motor end cap 44 and the gear end cap 35 may be secured by bolts 44a and 35a, respectively. A second motor bearing 46 has a hole 46a therethrough for receiving the motor core 39. A drive

end cap 48 may have a hole 48a for receiving a second motor bearing 46. A motor housing 56 protects the motor 24 and core 39. The housing 56 surrounds the motor 24 and is located _ between the motor end cap 44 and the drive end cap 48.

The shafts 31,34, and 50 act mechanically as single center shaft. Basically, all rotating elements rotate around a fixed center through shaft comprised of a number of mechanically joined components that act as a single mechanically locked, rigid, continuous center through shaft. The shafts 31,34,50 act as a single power-transferring shaft for driving power along a single central axis. For example, this fixed center through shaft is comprised of a series of mechanically joined elements including the gear end, the end cap and the first stationary shaft, three gear pins, the motor end cap, the motor housing and the drive end cap and the second stationary shaft. This configuration has many benefits including fewer components which makes it a simpler unit that is potentially less expensive, easier to maintain, and cheaper to repair.

As best seen in Fig. 2A, a bearing such as a spherical roller bearing 68,68a may be located at the first end 28 and second end 30 of the pulley drum 18. The bearings 68,68a surround the stationary shafts 34,50 and fit into the outer casing end plates 26a, 26c which have recesses 25a, 25b for receiving the spherical roller bearings 68,68a. A pair of shaft seals 94 abut a pair of plastic seals 92. The plastic seals 92 abut a pair of bearing seals 70 which act in cooperation to seal the drum 18. Other shaft sealing members 86 such as 0-rings 88 may be also present. In addition, the sealing member 86 may include an outer metal bearing seal 90 over a plastic seal 92 that fits over a shaft seal 94 contained within the recess in the outer casing end plates. Alternatively, the sealing members 86 may consist of a sealing gel.

Referring to Fig. 4, a controller 72 is preferably capable of varying the speed of the conveyor belt 10 between 20 and 200 feet per minute, although faster and slower speeds are contemplated. The central function of the controller 72 is to regulate the speed and direction and

allow constant speed control regardless of motor load. The controller 72 may be mounted directly to the conveyor system 5 or be remotely mounted. Preferably, the controller 72 has a National NEMA 4/12 stand alone enclosure to provide maximum protection and safety. The controller 72 may also have a speed control output which is accurate +/-. 5% of the desired set speed. Further, the controller may control the conveyor belt's preset belt advance lengths, start points, stop points, and pause points. The configuration of the controller 72 also provides for maximum efficiency, overload protection, stall protection, size advantage, and constant torque through the full range of speeds.

A digital front end with programmable logic controls (PLC) or personal computer controls may also be used to maintain constant speed under varying loads. Further, a removably connected digital DC controller plug-in may be provided for dynamically changing the speed of the conveyor. In addition, suitable connections for serial input/output connector such as RS232, RS422, RS485 or analog connector including a 0-10 volt DC or 4-20 ma connector may be supplied. In short, the conveyor system may be capable of any variable speed from 0 RPM to the maximum design RPM of the DC motor.

As shown in Figure 2, a removably connected tachometer readout 58 may also be provided on the conveyor system 5. The sensor for the tachometer is preferably part of the Hall effect sensor. Preferably, the tachometer 58 may be a digital LED system. The motor 24 may also have a switch or control input 56 for selectably reversing the direction of travel of the conveyor belt 10. The switch 56 may provide electrically switched on-the-fly reverse motion to the conveyor system 5.

The conveyor system 5 also preferably has a built in internal feedback system 80 for RPM and motor core position as a product of the Hall effect device 27. The feedback system 80 also allows the conveyor system 5 to maintain constant speed under varying loads.

For example. one way the feedback system 80 does this is by determining armature position within the motor and then calculating the number of RPMs of the drum 18. _ The Hall effect device or sensor 27 is operably connected to the motor controller 72 and operably associated with the pulley drum 18 for providing a control signal. The Hall effect sensor further allows for smooth transitions between starting and stopping, as well as, soft starting and stopping of the brushless DC motor 24 and serves as source for the tachometer 58.

For example, the motor 24 has a fixed number of poles, and the Hall effect sensor 27 senses the position of a given pole at a given point in time to determine the relative position of the pulley drum 18. The DC motor 24 also may act as a servo with aid of the Hall sensor 27 to incrementally move and advance the conveyor belt 10 forward and stop.

Hall effects are magnetic sensors 27 preferably built into the core 39 or rotor of the motor 24. The sensor 27 senses the rotor's position relative to the stator and sends a signal to the controller 72 telling the controller when to send power to the stator. This causes the shaft 31 of the motor 24 to turn.

Preferably, as shown in Fig. 6, the gear assembly 36a includes a cycloidal gear arrangement or reducer 61 which acts in communication with the motor shaft 31. The gear arrangement 61 includes two main disks 74a, 74b having offset elliptical rotations. The two disk system is used to increase torque capacities and offer an exceptionally smooth vibrationless drive. For example, at least 2/3 of gear arrangement's teeth share the shock of overload, and each tooth is cycloidally shaped so it cannot be sheared off. The cycloidal gear arrangement also has a unique capacity for frequent stop-start and severe reversing. Thus, flywheel (WR2) effect in the reducer 61 may be reduced to a minimum, so that it responds quickly in these applications. The shear-free cycloidal teeth also make the reducer 61 ideal for those applications which quickly wear out competitive reducers. Moreover, although the cycloidal reducers 61 may be

considerably smaller than conventional reducers, they don't sacrifice efficiency in the higher rations as other compacts must. Further, the reducer's smooth, almost frictionless operation may all but eliminate the conventional limitations due to heat.

Figure 7 is a graph showing the torque graphed as a function of speed in terms of RPMs and of amperage for the motor of the present invention. As is shown, it can be seen that the torque may have a relatively flat and generally smooth output curve over the full speed range of the system. This flat torque over varying speeds is a function of the motor, Hall senser and controller. The preferred motor, Hall senser and controller combination will deliver a flat torque at maximum torque over the entire speed range of the motorized pulley.

Although the best mode contemplated by the inventors of carrying out the present invention is disclosed above, practice of the present invention is not limited thereto. It will be manifest that various additions, modifications and rearrangements of the features of the present invention may be made without deviating from the spirit and scope of the underlying inventive concept. In addition, the individual components need not be fabricated from the disclosed materials, but could be fabricated from virtually any suitable materials. Furthermore, all the disclosed features of each disclosed embodiment can be combined with, or substituted for, the disclosed features of every other disclosed embodiment except where such features are mutually exclusive.

It is intended that the appended claims cover all such additions, modifications and rearrangements. Expedient embodiments of the present invention are differentiated by the appended subclaims.