Patent Publication Number: US-6705453-B2

Title: Method and apparatus utilizing servo motors for placing parts onto a moving web

Description:
This application is a continuation-in-part of prior application Ser. No. 09/620,867 filed Jul. 21, 2000, now U.S. Pat. No. 6,450,321. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for receiving discrete parts traveling at a speed and applying the parts to a web or other carrier traveling at a different speed. 
     BACKGROUND OF THE INVENTION 
     Disposable absorbent articles, such as disposable diapers, generally have been manufactured by a process where discrete parts or components of different materials, such as leg elastic, waist elastic, tapes and other fasteners have been applied to a continuously moving carrier web. Often, the speed at which the parts are fed from one place in the process onto a carrier web is different from the speed of the carrier web, therefore, the speed of the parts must be changed to match the speed of the carrier web to properly apply the parts without adversely affecting the process or the finished product. 
     Similarly, labels are typically placed onto articles when the speed at which the labels are fed into the process is not the same as the speed of the article to be labeled. Thus, the speed of the labels must be changed to match the speed of the carrier web to properly apply the parts without adversely affecting the process or the finished product. 
     Several different conventional methods for changing the speed of a part or component of material such that it can be applied to a continuously moving carrier web have been known to those skilled in the art. 
     For example, one method has been known as the slip cut or cut &amp; slip method. A web of material, which is traveling at a slower speed than the carrier web, is fed into a knife and anvil roll having a surface speed equal to speed of the carrier web. The material slips against the surface of the anvil roll until the knife cuts it into discrete pieces. The purpose of the slip is to ensure the correct amount of material is metered into the system at the desired tension prior to cutting. As the material is cut into the discrete parts, vacuum in the anvil roll is activated to hold the discrete part on the anvil without slipping, so that the discrete part is accelerated to the speed of the anvil roll. The anvil roll then carries the part to the point where the vacuum is released and the parts are applied to the carrier web while both the parts and the carrier web are traveling at the same speed. The problem with the above method is that the slip process is very sensitive to material properties and process settings. For example, when the coefficient of friction between the material and anvil roll is too high the material will elongate during the slip process. This elongation, if it occurs, can contribute to high variability in the final cut length and placement of the discrete part on the carrier web. 
     Another method has used festoons to reduce the speed of the carrier web to match the speed of the discrete parts of material to be applied to the web. An example of this method is described in U.S. Pat. No. 5,693,195 issued to Schmitz. The carrier web is temporarily slowed down to the speed of the parts with the excess portion of the carrier web gathering in festoons. The parts of material are then applied to the carrier web while both the parts and the web are traveling at the same speed. The festoons are then released allowing the moving web to return to its original speed. This method has two main drawbacks. First, the carrier web must be festooned and then released; this may damage or otherwise change the properties of the carrier web. Second, the storage system requires a large amount of space in typical disposables production systems because there is a direct relationship between line speed and storage space needed. 
     Another method has utilized a cam actuated follower arm. The cam actuated follower comprises a cam follower at one end of the arm and a holding plate at the other end of the arm. The cam follower remains in contact with a fixed cam which is mounted concentric with the instantaneous center of rotation of the holding plate. As the holding plate rotates, its radial distance from the center of rotation is increased and decreased to change the surface speed of the holding plate. The discrete parts of material are placed on the holding plate when it is at its smallest radius so that the speeds match. The plate then extends radially enough during the rotation to match the speed of the plate to the speed of the carrier web. At this point the discrete parts are transferred to the carrier web. This method has two main drawbacks. First, the plate is designed to match the curvature of one radius, not both. This means that either the pick-up of the discrete part or the transfer of the discrete part, or both, will occur across a gap for some part of the transfer. This can lead to a loss of control of the discrete part, which impacts handling of parts under tension, such as leg elastics. Second, to achieve the desired change in speed, the mechanical elements typically used, such as cams or linkages, become fairly large to stay within acceptable design limits for accelerations and rise angles. This size leads to increased cost and reduced flexibility, as the unit must be redesigned for each application. 
     Another method has utilized noncircular gears to change the speed of a transferring device. The means rotates at a constant radius, but the rotational velocity is varied between a minimum and a maximum to pick up the discrete part at its speed and place the part on the carrier web at its speed. This eliminates the size issues and speed or gap mismatch issues, but relies on mechanical means to achieve the change in rotational velocity. The drawback of this is that new transmission parts (gears or other means) are required each time a change in product design occurs that changes placement pitch length, discrete part length, or other key factors. This can be expensive and time-consuming to change. An example of this method is described in U.S. Pat. No. 6,022,443 issued to Rajala and Makovec. 
     SUMMARY OF THE INVENTION 
     In response to the discussed difficulties and problems encountered in the prior art a new method and apparatus for receiving discrete parts traveling at a speed, changing the speed of the parts to match the speed of a carrier web or body, and applying the parts to the carrier has been discovered. 
     In one aspect, the present invention concerns an apparatus for receiving discrete parts traveling at a first speed and applying the parts to a carrier traveling at a second speed. The apparatus comprises at least one rotatable transferring device and one driving mechanism for each transferring device. Each rotatable transferring device comprises at least one shell segment configured to move along an orbital path through a receiving zone where the parts are received and an application zone where the parts are applied to the carrier. The carrier might comprise a continuous moving substrate web, or might be another apparatus such as a drum. The driving mechanism utilizes a programmable motor such as a servo motor to transmit rotational energy to the rotatable transferring device. The driving mechanism may transmit rotational energy to the rotatable transferring device through a direct connection or a transmission interposed therebetween. The transmission may include gear to gear contact or gearboxes. 
     In another aspect, the present invention concerns an apparatus for receiving discrete parts of an elastic material traveling at a first speed and applying the parts to a carrier traveling at a second speed. The parts of the elastic material might already be at the desired tension and elongation length when the apparatus receives them. On the other hand, the parts of the elastic material might be at a lower tension and elongation length than desired when the leading edge is transferred to the apparatus, but might be stretched during the transfer to the apparatus if the apparatus is traveling at a faster speed than the discrete parts. Alternately, the parts might be at a higher tension and elongation than desired when the leading edge is transferred to the apparatus, but can relax to the desired state if the apparatus is traveling at a slower speed than the discrete parts. The change in tension and elongation can be performed uniformly along the entire length of the discrete material part, or can be intentionally varied during the initial transfer by changing the speed of the rotatable transferring means. 
     In another aspect, the material fed into the transferring device may comprise a continuous web which might be cut into discrete parts while on the transferring device by a knife, hot wire, laser beam, or other method commonly known. Alternatively, the material fed into the system can be broken into discrete parts by acceleration of the rotatable transferring device. This breaking process can be aided by perforating the material at the desired break point prior to arriving at the receiving zone. 
     In another aspect, the discrete parts can have adhesive or other bonding material applied to them while traveling on the rotatable transferring device. The rotation speed of the transferring device can be controlled in register with a bonding material applicator such that the bonding material can be applied either intermittently or continuously as the rotatable transferring device rotates. 
     In another aspect, the discrete parts of material can be modified prior to placement on the carrier to aid in a final bonding process. This modification can come through heat addition, moisture addition, or other known method for altering material properties to aid in the bonding process. 
     In still another aspect, the programmable motors of the apparatus of the present invention can be arranged in a series wherein each of the motors and the transferring devices(s) actuated by each motor is aligned in relation to a common axis of rotation of all motors and transferring devices. 
     As compared to conventional methods, such as the cut &amp; slip method described above, for changing the speed of a discrete part so that it can be applied to a carrier, utilizing a programmable motor provides the ability to obtain greater changes in speed, to maintain constant speeds for a fixed duration, and to simplify the set-up process when changing from one product to another. Thus, the use of programmable motors can provide a more precise control of the length and placement of the part onto the carrier while offering great flexibility in the type of parts that are to be made. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more fully understood and further advantages will become apparent when reference is made to the following detailed description of the invention and the accompanying figures. The figures are merely representative and are not intended to limit the scope of the appended claims. 
     FIG. 1 representatively shows an isometric view of one example of an apparatus of the present invention. 
     FIG. 2 representatively shows a schematic side view of the apparatus in FIG.  1 . 
     FIG. 3 representatively shows a schematic side view of the apparatus used in the present invention arranged in series. 
     FIG. 4 representatively shows a perspective view of an apparatus according to the present invention comprising two transferring devices. 
     FIG. 5 representatively shows a perspective view of the apparatus shown in FIG. 4 including a cutting device. 
     FIG. 6 representatively shows a speed profile for a typical motor output. 
     FIG. 7 representatively shows an alternate speed profile for a motor output wherein one of the fixed speed regions has been changed to variable speed. 
     FIG. 8A representatively shows an alternate speed profile for a motor output wherein the rise time β has been decreased to allow for a non-optimal radius without changing the maximum or minimum rotational velocity in the system. 
     FIG. 8B representatively shows an alternate speed profile for a motor output wherein the maximum rotational velocity during the period of transition from receiving to application zone exceeds the average rotational velocity in the application zone to allow for a non-optimal radius. 
     FIG. 8C representatively shows an alternate speed profile for a motor output wherein the minimum rotational velocity during the period of transition from receiving to application zone is less than the average rotational velocity in the receiving zone to allow for a non-optimal radius. 
     FIG. 9 a  representatively shows a perspective view of an apparatus according to the present invention including an applicator for accomplishing a secondary process on the parts, and two transferring devices comprising multiple shell segments. 
     FIG. 9 b  is a side view of the apparatus shown in FIG. 9 a.    
     FIG. 10 representatively shows an isometric view of adjacent shell segments according to the present invention having grooved leading and trailing edges that mesh. 
     FIG. 11 representatively shows an isometric view of another embodiment of the present invention including a series of motors aligned with a common central axis and wherein each of the motors has a hollow rotatable shaft. 
     FIG. 12 representatively shows a plan view of the embodiment shown in FIG.  11 . 
     FIG. 13 representatively shows an isometric view of the embodiment shown in FIGS. 11-12 in combination with a cutting device as viewed from upstream. 
     FIG. 14 representatively shows an isometric view of the embodiment shown in FIGS. 11-12 in combination with a cutting device as viewed from downstream. 
     FIG. 15 representatively shows a side view of the embodiment shown in FIGS. 13 and 14. 
     FIG. 16 representatively shows an isometric view of another embodiment of the present invention including a series of motors aligned with a common central axis and wherein each of the motors has at least one stationary track rail and a movable rider. 
     FIG. 17 representatively shows a plan view of the embodiment shown in FIG.  11 . 
     FIG. 18 representatively shows a side view of the embodiment shown in FIGS. 16 and 17. 
     FIG. 19 representatively shows an isometric view of another embodiment of the present invention including a series of motors aligned with a common central axis and wherein each of the motors has a stationary inner stator and a rotatable outer rotor. 
     FIG. 20 representatively shows an isometric view of another embodiment of the present invention including a series of motors aligned with a common central axis and wherein each of the transferring devices follows an orbital path. 
     FIG. 21 representatively shows a plan view of the embodiment shown in FIG.  20 . 
     FIG. 22 representatively shows a side view of the embodiment shown in FIGS. 20 and 21. 
     FIG. 23 representatively shows an isometric view of the embodiment shown in FIGS. 20-22 including a cutting device as viewed from downstream. 
     FIG. 24 representatively shows an isometric view of the embodiment shown in FIGS. 20-22 including a cutting device as viewed from upstream. 
     FIG. 25 representatively shows a side view of the embodiment shown in FIGS. 23-24. 
     FIG. 26 representatively shows an isometric view of another embodiment of the present invention including a series of motors aligned with a common central axis and wherein each of the motors has at least one stationary planetary track rail and a movable rider. 
     FIG. 27 representatively shows an isometric view of another embodiment of the present invention including a stretching device. 
     FIG. 28 representatively shows an isometric view of another embodiment of the present invention including a rotating device. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a method and apparatus for receiving discrete parts traveling at a first speed and applying the parts to a carrier traveling at a second speed. The apparatus and method are particularly useful for applying any part to a carrier useful in the making of disposable absorbent articles or for placing labels onto articles. It is readily apparent, however, that the method and apparatus would be suitable for applying any part to a substrate web or carrier of parts. 
     Referring now to FIGS. 1 and 2, there is representatively shown an aspect of the invention wherein an apparatus generally indicated at  20  receives discrete parts  30  traveling at a first speed in the direction indicated by the arrow  91  associated therewith and applies the parts  30  to a carrier  80  traveling at a second speed in the direction indicated by the arrow  92  associated therewith. The illustrated example of the apparatus  20 , as representatively shown in FIGS. 1 and 2, further comprises a driving mechanism  61  for transmitting rotational energy to a driven mechanism  71 . The driving mechanism  61  includes a connection to the driven mechanism using any technique known to those skilled in the art such as, for example, gear to gear connection, transmission belting and pulleys, gearboxes, direct couplings, and the like or any combinations thereof. For example, in FIG. 1 the driving mechanism is connected to a driving gear  62  which transmits rotational energy to a driven gear  72  connected to the driven mechanism  71 . In use, the driving gear  62  engages and rotates the driven gear  72  which, in turn, rotates the transferring device  50 . 
     The illustrated example of the transferring device  50  comprises at least one shell segment  51  connected to the driven mechanism  71 . The shell segment  51  of the transferring device  50  can be connected to the driven mechanism  71  by any technique known to those skilled in the art such as, for example, bolts, screws, pins, keys and matching key ways, connector parts such as shafting or brackets, welding and the like or combinations thereof. For instance, the shell segment  51  shown in FIG. 1 is connected directly to the driven gear  72  by fitting the end of the shell segment  51  into a mating hole in the driven gear  72  and locking it into position with a pin. Similarly, other components of the apparatus  20  can be connected together employing the above described assembly techniques. 
     The dimensions of the shell segment  51  may vary depending upon the desired output of the apparatus  20  and the size and shape of the discrete articles  30  being transferred. The shell segment  51  may comprise a crescent-shaped member having an outer, peripheral arc length spanning from about 5 degrees to about 340 degrees, an outer radius ranging from about 25 mm to about 500 mm, and a width ranging from about 50 mm to about 750 mm. As the driven mechanism  71  rotates, the transferring device  50  travels in the direction indicated by the arrow  93  as shown in FIG.  2 . The circumferential, outer peripheral surface of the shell segment  51  defined by an outer radius, travels along and defines an orbital path that passes through a receiving zone  21  and an application zone  23 . The receiving zone  21  and the application zone  23  are defined by the respective regions of the orbital path traveled by the shell segment  51 . 
     The illustrated example of the driving mechanism  61  includes a rotatable circular driving gear  62  connected to an input shaft  63 . In this example, the input shaft  63  is the output shaft of the motor  64 . The driven mechanism  71  is placed parallel to the driving mechanism  61  such that the driving gear  62  meshes with the driven gear  72  using gear set-ups known to those skilled in the art. In use, the motor  64  rotates the input shaft  63  which rotates the driving gear  62  which, in turn, rotates the driven gear  72  and transferring device  50 . 
     Alternatively, the driven mechanism  71  may include any mechanism known to those skilled in the art by which rotational energy can be conducted from one shaft to another such as, for example, v-belts, timing belts, continuous chains and the like or combinations thereof. Further, the driven mechanism  71  may include any mechanism known to those skilled in the art by which input velocity can be variably modified to an output source such as, for example, cams, linkages, and the like or combinations thereof as long as the changes in rotational speed are substantially created by the motor  64 . 
     It will be further appreciated that the method and apparatus  20  of the invention can utilize one or, in the alternative, two, three or more combinations of transferring devices  50 , driven mechanism  71 , driving mechanism  61  and motor  64  in series to achieve the desired application of the discrete parts to the carrier. The different combinations may allow the use of a continuously moving web to supply the discrete parts. In addition, greater speed ratio differentials may be achieved by using combinations of transferring devices, driven mechanisms, driving mechanisms and motors in series. 
     It will be further appreciated that the method and apparatus  20  of the invention, when used in series, do not need to operate at the same receiving zone  21  and application zone  23 . For example, referring to FIG. 3, there is representatively shown one apparatus  20 A comprising one transferring device  50 A connected to a motor  64 A by a driving gear  62 A and driven gear  72 A and a second apparatus  20 B comprising one transferring device  50 B connected to a motor  64 B by a driving gear  62 B and a driven gear  72 B. Apparatus  20 A uses receiving zone  21 A to accept parts  30  from a drum  43  while apparatus  20 B uses receiving zone  21 B to accept parts  30  from the same drum  43  at a different rotational position on said drum. 
     Another aspect of the invention shown in FIG. 4 comprises an apparatus  20  receiving discrete parts  30  of a web of an material  31  traveling at a first speed in the direction indicated by the arrow  94  associated therewith and applies the parts  30  to a carrier  80  traveling at a second speed in the direction indicated by the arrow  95  associated therewith. The illustrated example of the apparatus  20  comprises two rotatable transferring devices, represented by  50 A and  50 B, for receiving and applying the parts  30 . The apparatus  20  further comprises a driving system  60  having two driving mechanisms  61 A and  61 B, each of which includes a motor  64 A,  64 B and a driving gear  62 A,  62 B for transmitting rotational energy to the driven mechanism  71 A,  71 B represented by the driven gear  72 A,  72 B. 
     As illustrated in FIG. 4, each transferring device  50 A and  50 B comprises a shell segment  51 A,  51 B connected to a driven gear  72 A,  72 B. As each gear rotates, the transferring devices  50 A,  50 B travel in the direction indicated by the arrow  96  associated therewith. In use, the circumferential, outer peripheral surface of the shell segments  51 A,  51 B travels along and defines an orbital path that passes through a receiving zone  21  and an application zone  23  defined by the respective regions of the orbital path traveled by the shell segments  51 A,  51 B of transferring devices  50 A and  50 B. 
     The size and shape of the shell segments  51 A and  51 B may vary as the number of shell segments per transferring device changes. For example, if the apparatus includes two transferring devices as representatively illustrated in FIG. 4, each shell segment  51 A and  51 B may have an outer peripheral arc length which spans from about 5 to about 175 degrees of the orbital path of the transferring devices  50 A and  50 B. 
     Each driven mechanism  71 A,  71 B may include any mechanism known to those skilled in the art by which rotational energy can be conducted from one shaft to another such as, for example, v-belts, timing belts, continuous chains and the like or combinations thereof. Further, the driven mechanisms  71 A,  71 B may include any mechanism known to those skilled in the art by which input velocity can be variably modified to an output source such as, for example, cams, linkages, and the like or combinations thereof as long as the changes in rotational speed are substantially created by the motor  64 . Alternatively, a first driven mechanism may connect to a first transferring device using a first shaft from a driven gear, and a second driven mechanism may be connected to a second transferring device using concentric shafting around the first shaft. 
     The apparatus  20 , as representatively illustrated in FIG. 5, may further comprise a cutting device  40  comprising a pinch knife cutter  41  and a knife anvil  42  to sever the continuously moving web of material  31  into discrete parts  30  prior to or concurrent with the transfer of the discrete parts to the shell segments  51 A,  51 B of the transferring devices  50 A,  50 B. The pinch knife cutter  41  may comprise a rotary cutter as shown or any other mechanism known to those skilled in the art capable of severing a web of material into discrete parts. In certain aspects of the invention, the knife anvil  42  may be omitted and the pinch knife cutter  41  can be made to sever the web as it is held on the shell segment of the transferring device. Alternately, the continuously moving web of material may be placed directly on the shell segments of multiple transferring devices so that the web lies on multiple segments at once allowing for the planned acceleration of one device to generate a force necessary to sever a single part from the web. Such severing may be facilitated by perforating the web upstream of the receiving zone so that the parts break at a desired perforation during acceleration. 
     For receiving the parts in the receiving zone, the transferring device, as representatively illustrated in the various configurations of the invention, may further include a gripping mechanism so that the outer concave surface of the shell segment can capture a part in the receiving zone and transport the part to the application zone. For this embodiment, the gripping mechanism may include a vacuum that can be selectively imposed through ports in the shell segment leading to the outer concave surface. For instance, the vacuum may be activated in the receiving zone to seize the parts and deactivated in the application zone to release the parts to the carrier. In this manner, positive control is maintained over the parts at all times during the transfer process. Alternatively, the gripping mechanism may include any technique known to those skilled in the art for gripping and releasing parts such as, mechanical clamps, electrical clamps, magnetic clamps and the like or combinations thereof. 
     For transferring the parts to the carrier in the application zone, the apparatus may comprise any of a variety of options known to those skilled in the art such as, adhesive applied on the part, adhesive applied on the carrier, electrostatic charge between the part and carrier, vacuum on the carrier and the like or combinations thereof. Alternately, the transfer can include the generation of a weld between the part and the carrier by any of a variety of means known to those skilled in the art such as, pressure generation at a nip formed between the shell segment and the carrier at transfer, interaction between a pattern on the shell segment and an ultrasonic horn behind the carrier at transfer, and the like, or combinations thereof. In addition, in order to aid the welding process, the part may be modified on the shell segment by energy addition using any mechanism known to those skilled in the art such as, for example, hot air currents, ultraviolet lighting, laser bombardment and the like or combinations thereof 
     The use of a programmable motor in the apparatus, as representatively illustrated in the various aspects of the invention described above, provides an inexpensive and adaptable method for receiving parts  30  traveling at a speed and applying the parts to a carrier  80  traveling at a different speed. The variable angular velocity is produced by varying the current supplied to the motor. Since the driven mechanism is coupled to the output of the motor, changes in the angular velocity and position of the motor directly correlate to changes in the angular velocity and position of the transferring device. The current supplied to the motor can be controlled using any of a variety of a methods for programming motors known to those skilled in the art such as, standard cam curve functions, a reference data table containing reference points, desired motor encoder points, and the like or combinations thereof. 
     The means of supplying the rotational movement required can be achieved in a plurality of methods to those skilled in the art. The programmable electric motors can be driven from any known power source that is capable of delivering a modulated signal such that the motor torque can be varied proportionally. The number of motors included per a transferring device can be any suitable number. Each motor attached to a single transferring device can be supplied by one or more power sources capable of delivering a modulated torque signal. The torque signal is typically an electrical current which may be fed to the individual motors by separate power supplies or by a single power supply and controlled by a plurality of methods to those skilled in the art. 
     The actual position of the transferring device can be controlled in a plurality of methods to those skilled in the art The control system demonstrated utilizes a programmable system that incorporates a position feedback from the transferring device and motor. The position feedback device on the transferring device, or motor, may or may not be required if the position of the transferring device can be inferred by other means known to those skilled in the art. The typical position transducer is an encoder, or resolver based system, but any system that can be constructed to provide the actual position, or the inferred position of the transferring device can be used. 
     The demonstrated control system is one of many kinds, models, and technologies that can be used to supply the proportional signal to the motor power supplies that will generate the modulated torque signal. 
     The control system may or may not be integrated into the motor power supply, The control system, along with the motor power supply, may or may not be integrated into the motor itself. The control system may or may not be digitally controlled, and may be constructed in various methods, and configurations known to those skilled in the art. The control system, power supplies, feedback devices, and motor devices, and any other components required for the purpose of providing rotational movement are hereafter referred to as the “drive system” for the transferring device. 
     The drive system will be capable of continuously controlling the position of the transferring device, and allowing the transferring device to stay in phase to a given position on the recipient product, web, or host machine. The drive system will be capable of following speed transitions or position variations on the recipient product or web, by phasing itself, when necessary, to the recipient product, web, or host machine, with or without operator intervention. The drive system will allow for the registration of the patch on the transferring device in relation to the recipient product or web, either upstream or downstream of the transferring device. 
     The drive system may be capable of providing for a plurality of control methods and algorithms known to those skilled in the art for the purpose of providing motion and position control that will allow the transfer of a patch to a recipient product or web. The drive system may be capable of changing the patch length with or without operator intervention, for the purpose of varying product sizes or continuous patch length, or position variation control. The position reference for the drive system maybe a pre-calculated cam profile, continuously calculated profile, or any positional trajectory generation algorithm known to those skilled in the art and may be either digital or analog based. The motion trajectory for the transferring device may be based on a pre-calculated profile or a profile that is modified by the speed of the recipient product or web. 
     The speed profile of a typical motor setting is representatively illustrated in FIG.  6 . As shown, the programmable motor  64  used to drive the transferring device  50  of the present invention can provide variable angular velocities including periods where the velocity remains constant for a fixed duration. These constant velocity dwell times can be advantageous in the receiving zone  21  and the application zone  23  particularly when the pick up and transfer occurs over substantial arc lengths of contact. Alternatively, one or more of the constant speed regions can be changed to a controlled variable speed region as representatively illustrated in FIG.  7 . This would enable the part  30  to be picked up in the receiving zone  21  at a variable speed, which, when the part  30  is elastic, would allow tensions to be varied incrementally therein which may be desirous in certain product features. In another example, the constant speed of the motor  64  in the application zone  23  can be such that the corresponding speed of the transferring device is different from speed of the carrier at transfer. Such speed variations generate tension in the part  30  by incrementally transferring the part  30  in a controlled manner from one means traveling at one surface speed to a second means traveling at a second surface speed. 
     It will be further appreciated that the velocity of the transferring device  50  outside of the application zone or the receiving zone can be tailored to aid the performance of secondary processes including adhesive application, printing of identification or registration marks, application of bonding aids, moisture addition and the like and combinations thereof Such changes in velocity may be beneficial by presenting specific velocity profiles or even additional periods of constant velocity, which would allow for more precise interaction with the secondary processes being performed. 
     Programmable motors, such as those used in the present invention, can be purchased from any number of suppliers of programmable motors such as Rockwell Automation, located in Milwaukee, Wis. Further, the program inputs to the motors can be generated by one of ordinary skill in the art if provided with the analytical representation of the desired output function as representatively illustrated in FIG.  6 . For instance, the creation of the electronic cam profile for the motor can be developed by first determining the key input variables. The key input variables are based on desired product features, the base design of the apparatus  20  and the desired cycle speed of the apparatus  20 . Secondly, the radius of the outer surface of the transferring device  50  is determined. Once the radius is determined, the required cam inputs of rotational velocities, distances traveled and time available for acceleration can be calculated, which serve as the input to the cam profile generator. For example, in a system with the following inputs: 
     N=the number of transferring devices  71  used in the apparatus  20   
     H=the number of shell segments  51  per transferring device  71   
     L s,parts =distance from lead edge of first part  30  received in a given transfer to transferring device  50  to lead edge of part  30  received in the next cycle of transfer to a transferring device  50  in the apparatus  20   
     L s,product =distance from lead edge of first product zone on carrier  80  to which parts  30  are applied in a given transfer from transferring device  50  to lead edge of product zone on carrier  80  to which parts  30  are applied in the next cycle of transfer from a transferring device  50  in the apparatus  20   
     V min =average surface speed of the shell  51  on the transferring device  50  in receiving zone  21   
     V max =average surface speed of the shell  51  on the transferring device  50  in application zone  23   
     τ=cycle time of a given lane of product making 
     τ R =time in receiving zone  21 , typically of value τ when V min =incoming speed of parts  30   
     τ A =time in application zone  23 , typically of value Ratio * τ when V max =speed of carrier  80  The following dependent variables can be computed: 
     Ratio=L s,parts /L s,product    
     Radius=distance from effective center of rotation of transferring device  50  to outer surface of shell  51  on transferring device  50   
     τ TRANS =time in transition from V min  to V max =N*τ−τ R −τ A =(N−1−Ratio) *τ 
     ω min =average angular velocity of transferring device  50  in receiving zone  21 =V min /Radius 
     ω max =average angular velocity of transferring device  50  in application zone  23 =V max /Radius 
     θ min =ω mm *τ R =ω min  *τ 
     θ max =ω max *τ A =ω max * Ratio *τ 
     θ transition =2*π/H−θ min −θ max =2*π/H−ω min *τ−ω max * Ratio *τ 
     The Radius may be determined by assuming that the average angular velocity, ω ave , of the transferring device  50  during the transition from the receiving zone  21  to the application zone  23  is equal to (ω min +ω max )/2. This means that the distance traveled during the transition θ transition =ω ave *τ TRANS . However, θ transition  must also be equal to 2*π/H−θ min −θ max . Consequently, by setting the two equations for θ transition  equal to one another the following expression for Radius is defined. 
     
       
         Radius=(L s,part *(N+1−Ratio)+L s,product * (N−1+Ratio))* H/(4*π)  
       
     
     It is important to note that L s,part  as defined can be different from the overall length of the par, for example, when the edges of the part are cut at some angle which is not perpendicular to the direction of flow of the part. The above equations and parameters must be solved slightly differently to account for this. 
     Now, given the inputs, one of ordinary skill can determine τ TRANS , ω min , ω max , θ min , θ max , and θ transition  which are typical inputs needed for electric cam software programs. The generic cam programs would then create the input table for the motor  64 . Note that the Radius is an optimal radius, and not the only possible radius for the set of inputs. The Radius is optimal because it uses the entire transition time for changing the angular velocity of the transferring device  50 . By changing the Radius, the actual amount of time required to change speed must change or else the combined conditions of change in angular velocity and change in angular acceleration will not be met. The amount by which the Radius can deviate from the optimum can be changed from optimal depends upon the torque requirements of the system under the new accelerations at the given speed and the capability of the selected motor  64 . 
     Alternately, one of ordinary skill could generate the input table for the motor without the aid of software programs. For example, the cam profile for cycloidal motion having dwells of constant velocity comprises a minimum velocity equal to ω min , a change in velocity, Δω, equal to ω max −ω min , and a rise time β of the motion equal to τ TRANS /2. The resulting function of angular position is as follows: 
     θ act =ω min *T when 0≦time in cycle, T≦τ R    
     θ act =ω min *T+½*Δω*β*((T−τ R )/β−sin ((T−τ R )*π/β)/π)when π R &lt;T&lt;π R +β 
     θ act =ω min *T+½*Δω*β+ω max *(T−τ R −β)when τ R +β≦T≦τ R +β+τ A    
     θ act =ω min *T+½*Δω*β+ω max *τ A +½*Δω*β*((T−τ R −β−τ A )/β−sin((T−τ R −β−τ A )*π/β)/π) when τ R +β+τ A &lt;T≦τ 
     Profiles other than the cycloidal profile can be found in Machinery&#39;s Handbook, the 25th Edition. 
     If a radius is chosen for the transferring device that is not optimum, the transferring device will accomplish the desired changes in velocities, however, the timing for such changes will not correspond to that which is desired. For instance, if the Radius is slightly greater than optimal, using the equations above, the actual distance traveled during the transition is less than needed to position the transferring device  50  at the start of the application zone  23  even though the transferring device  50  achieves the desired angular velocity. 
     There are at least three possible ways to achieve speed profiles accommodating pick up and transfer using a non-optimal Radius. First, the rise time β can be decreased by spending more time at ω min   as shown in FIG.  8 A. Secondly, as shown in FIG. 8B, the maximum angular velocity in the transition zone can be greater than the ω max  in the application zone  23 . Thirdly, the minimum angular velocity in the transition zone can be less than the ω min  in the receiving zone  21  as shown in FIG.  8 C. 
     Using the same cam formulas, one can determine the maximum accelerations generated during the motion using the same family of cam profiles. For example, for the cycloidal profile used above, the peak acceleration is (Δω*π)/(2*β). This is important because, for high speed applications, the limiting design factor in the apparatus  20  is motor  64  torque capability at the desired angular velocities. One of ordinary skill in the art can determine total torque requirements for the apparatus  20  for a given application based on the masses and radii of gyration for the different components of the apparatus  20  and the expected accelerations. 
     As compared to conventional methods for changing the speed of a discrete part so that it can be applied to a continuously moving carrier (such as the slip cut method described above), the use of programmable motors provides the ability to obtain greater changes in speed and to maintain constant speeds for a fixed duration. The fixed speed dwell achieved by programmable motors can be accurately and quickly generated to control the length and placement of the parts. In comparison to the noncircular gear method described above, the use of programmable motors provides the ability to change the profile at will without requiring the fabrication of new parts. 
     For example, in the various aspects of the invention, the profile generated by the programmable motor  64  is analytically designed such that the rotatable transferring device  50  receives the parts  30  in the receiving zone  21  while maintaining a constant surface speed substantially equal to the speed of the parts  30 . Moreover, the output profile of the motor  64  is designed such that the surface speed of the rotatable transferring device  50  changes to a second constant surface speed as the rotatable transferring device  50  moves from the receiving zone  21  to the application zone  23 . The term “surface speed,” as used herein, refers to the speed of the circumferential, outer peripheral surface of the shell segment  51 . The output profile of the motor  64  can be designed such that the speed of the parts  30  being transferred is substantially equal to the speed of the carrier  80  as the parts are applied to the carrier in the application zone  23 . The surface speed of the shell segment  50  is maintained substantially constant in the receiving zone  21  and in the application zone  23  from at least about 0 to about 300 degrees of rotation, desirably from about 5 to about 300 degrees of rotation, and more desirably from about 5 to about 240 degrees of rotation of the transferring device  50 . In addition, the surface speed increase or decrease of the shell segment  51  as it moves from the receiving zone  21  to the application zone  23  defines a speed ratio of from at least about 100:99 to about 50:1, desirably from about 20:19 to about 25:1, and more desirably from about 10:9 to about 20:1. The term “speed ratio”, as used herein, defines the ratio of the surface speed of the shell segment  51  as the parts  30  are applied to the carrier  80  in the application zone  23  to the surface speed of the shell segment  51  as the parts  30  are received in the receiving zone  21 . 
     It has been described above how the required torque and angular speed of the apparatus determine the needed motor capability. For high speed applications common in the manufacture of articles such as diapers, training pants, among other uses, the peak torque requirements of the apparatus  20  combined with the resulting acceleration at the motor  64  will require very high torque to inertia properties in the motor  64 . Motors capable of such flux densities are typically of rare earth permanent magnet design or more powerful, and can be purchased from manufacturers of motors such as Rockwell Automation located in Milwaukee, Wis. 
     In some embodiments it may be necessary to have more than one shell segment per transferring device driven by a single motor, particularly where the process includes secondary operations that are preferably performed at constant speed (see below). It may also be necessary to have multiple shell segments per transferring device in order to increase the radius from the center of rotation to the arcuate outer surface of the shell segments. The radius of a transferring device having a single shell segment may be so small that secondary parts of the design (such as porting airflow for vacuum across the shell segment) may be impractical. Based on the equation above for determining Radius, adding shell segments per transferring device results in an increase in Radius. For example, increasing the number of shell segments per transferring device from one to three triples the Radius. 
     Additional shell segments also result in an increase in motor torque which is determined from the following expression. 
     
       
         T=I motor *α motor +I load * α motor *(N driving /N driven ) 2    
       
     
     where 
     I motor —is the moment of inertia of the motor including anything connected directly to the motor shaft. 
     α motor —is the angular acceleration of the motor 
     N driving /N driven —the ratio of the number of teeth on the driving gear to the number of teeth on the driven gear. 
     I load —is the moment of inertia of the load (including the transferring device). 
     The additional shell segments result in an increase in mass moment of inertia of the transferring device, I load . Inertia is a direct function of mass and radius of gyration squared. For a transferring device having three shell segments, the mass can be expected to approximately triple and the radius of gyration can be expected to nearly double. Consequently, the moment of inertia of the transferring device can be expected to be at least ten to twelve times the inertia of an equivalent system having a single shell segment. The increase in inertia results in a decrease in the rotational velocity by a factor of three in a system having three shell segments per transferring device, consequently, the gear ratio, N driving /N driven   is increased by a factor of three in order to maintain the required motor acceleration. Overall, the resultant torque requirement for the system having three shell segments per transferring device is 11% greater relative to a transferring device having one shell segment per transferring device. Given that motor capability is the key limiting design factor, an increase of 11% in required torque can be significant and can potentially limit the capacity and application of the apparatus. 
     There is no restriction on the number of shell segments per motor besides space and inertial concerns, however, the arrangement pattern of multiple devices is limited. For instance, a transferring device having two shell segments per motor cannot be arranged such that any two shell segments on one transferring device are adjacent to one another in sequence without at least one shell segment from a separate transferring device driven by a separate motor interposed between them. FIGS. 9 a  and  9   b  portray an apparatus according to the present invention including an applicator for performing a secondary process on the parts and two transferring devise  150  and  250 , each having multiple shell segments. Transferring device  150  comprises three shells  151 A,  151 B, and  151 C and transferring device  250  comprises three shells  251 A,  251 B, and  251 C. Each transferring device is driven by a separate motor  164 ,  264 . As shell segment  151 A of transferring device  150  collects a part in the receiving zone  21 , the surface speed of shell segments  151 A,  151 B and  151 C are each equal to the receiving speed while the surface speeds of shell segments  251 A,  251 B, and  251 C of transferring device  250  are each equal to either the application speed or some other transitional speed. 
     Transferring devices comprising two or more shell segments are particularly beneficial where the process includes secondary processes where it is necessary for the part to be moving at a constant speed. As previously described, a secondary process step can be performed on the part such as adhesive application, printing, heating, or moisture application at any point between the receiving zone and the application zone. However, it is preferred to perform the secondary process while the part is moving at constant speed. In applications where the parts are received as a continuous web with no scrap separating the parts during separation, it is preferred that no gaps occur between adjacent shell segments during the transfer in the receiving zone. For instance, where the secondary process involves the application of an adhesive, it is preferred that the parts move at a constant speed during the application with no gaps in between parts so that the metering rate of the adhesive can be constant and not intermittent. 
     In order to perform a secondary process on the part at a constant speed with no gaps, the secondary process can be performed on the part before the transferring device starts to accelerate. In other words, the time at the receiving speed is lengthened so that the full arc length of the shell segment of the transferring device (assuming that the entire length of the part is required) passes through the process. For example, if the process involves application of an adhesive, then the entire arc length passes underneath the nozzle of the adhesive applicator. This presents a challenge for a transferring device comprising a single shell segment driven by a single motor since the sum of the receiving time, the application time, and the time for the secondary process might exceed the total cycle time. This problem may be resolved by adding a second transferring device having a single shell segment driven by a separate motor or by using a transferring device having more than one shell segment per transferring device. 
     In the process, generally, as one shell segment finishes receiving a part, the next shell segment in sequence starts receiving a part Generally, the parts entering the transferring device are part of a continuous web having no spacing in-between at the receiving zone. Consequently, in order to have a no gap situation, shell segments in the receiving zone should have no gap between them. However, in reality, variability in motor positioning, head dimensions, gear backlash, etc. can cause the position of the transfer device to have some variability in rotational position resulting in gaps or even forcible contact therebetween. The above problem can be resolved by the embodiments of the present invention described hereinbelow. 
     First, the shell segments can be fabricated to be a little shorter in arc length than the part to be received, and then the devices can be brought close but not contacting each other. This avoids contact, but does not allow for complete control of the lead and trail edges of the part. This may or may not impact product quality, depending on the part properties. Second, the shell segments can have a shock-absorbing structure on the lead and/or trail edges, so that contact does not generate damage. Depending on the desired cycle life of the transfer device, this might be as simple as placing a compressible foam or as complex as a spring-loaded wall. Third, the shell segments can have mating surfaces which allow the devices to coexist radially and tangentially but not axially. As shown in FIG. 10, shell segments  151 A and  215 A can have grooved or otherwise modified leading and trailing edges that mesh with similarly modified edges on adjacent shell segments. 
     It should be understood by one skilled in the art that the embodiments of the present invention having a driven mechanism placed parallel to a driving mechanism described hereinabove are limited to a number of transferring devices and/or a number of heads per a transferring device and/or a number of independent motors per a transferring apparatus. First, this is due to the increasing mechanical complexity associated with providing sufficient stiffness for the shafts rotating the transferring devices because in order to provide more than two rotating transferring devices sharing the same axis of rotation per an apparatus there will be more than one rotating transferring device per a side of the carrier web and the shafts driving the transferring devices located on the one side of the carrier web will be arranged concentrically to each other and thus, the diameters and/or wall thicknesses of the concentric shafts will diminish as the number of transferring devices on the one side of the carrier web increases. Second, as described therein above, as the number of shell segments per a transferring device increases, the torque requirements for the system increases. Third, the number of independent motors driving a transferring device is limited by the physical space available around the transferring device. 
     Referring now to FIGS. 11-12 showing an apparatus  500  of the present invention having a series of four motors  502  aligned with a common axis  504 . The number of motors can be any suitable number. Each of the motors  502  has an outer stationary stator  518 , an inner rotatable rotor  516 , and a hollow shaft  512  rotatable with the inner rotor  516 . The hollow shaft  512  can be positioned on bearings  514  to enable the hollow shaft  512  to rotate in relation to the stationary central shaft  510 . The bearings  514  can be any suitable bearing. In order to maintain the stator  518  stationary, the stator  518  can be connected to the stationary central shaft  512  via a bracket  520 . The motors  502  can be purchased from Kolhmorgen Inland Motor of Radford, Va. 
     Each of the hollow rotatable shafts  512  is linked to a transferring device  522  via a rigid transmitting mechanism  524  to enable the transferring device  522  to rotate together with the hollow rotatable shaft  512  around the common axis  504 . The rigid transmitting mechanism  524  can be attached to the hollow rotatable shaft  512  and the transferring device  522  by any suitable means. The transferring device  522  can be supported by a bearing  526  which can be supported by the stationary central shaft  510 . The bearing  526  can be any suitable bearing. Alternatively, if desired, the transferring device  522  can be attached to a second motor  502  to provide increased driving capability and/or structural support for the transferring device. Further, alternatively, the transferring device  522  can be driven by any desirable number of motors. 
     FIGS. 13-15 illustrate an example of how the apparatus  500  can be used in combination with the cutting device  40  (previously shown in FIG.  4 ), similarly in all or any aspects to the cutting application described in detail hereinabove, including the alternative omission of the anvil roll  42  and the alternative severing of the material web  31  by a speed differential between adjacent transferring devices. 
     FIGS. 16-18 illustrate another embodiment of an apparatus  550  of the present invention forming a series of nine motors  551  aligned in relation to the central common axis  556 . The motor  551  is generally known as a linear motor having a stationary track  552  forming a path  553  and at least one rider  554  movable on the stationary track  552  on the path  553 . The motor  551  can be any suitable linear motor, including linear motors available from Anorad Corporation of New York. For example, the stationary track  552  can include armature windings and/or magnetic materials. The rider  554  can be a permanent magnet, coils, or combinations thereof. The rider is attached to the transferring device  555  for moving the transferring device  555  around the central common axis  556 . The number of riders attached to the transferring device can vary from a single rider  554  to a multiplicity of riders  554 , either controlled independently or jointly. As shown in FIGS. 16-18, each transferring device  555  is moved by three riders  554 . 
     FIG. 19 illustrates another embodiment of an apparatus  600  of the present invention forming a series of twelve motors  602  aligned in relation to a central common axis  604 . The motor  602  can be any conventional motor having a rotatable outer rotor  606  and a stationary inner stator  608 . As shown, each stator  608  is attached to a stationary central shaft  610 , however, the motors  602  can be aligned without the use of the central shaft  610 , for example, by connecting the motors  602  sideways to each other, directly or indirectly, via inner stationary stators  608 . Each of the outer rotors  606  can be directly or indirectly attached to one or more of the transferring devices  550  for moving the transferring device in a programmed motion. 
     Alternatively, the apparatus of the present invention can include other types of programmable electrical motors suitable to provide a rotational motion of the outer component of the motor. For example, the motors wherein the stator and rotor are disposed parallel to each other as opposed to the concentric arrangements of the motors described therein above. 
     FIGS. 20-22 illustrate another embodiment of an apparatus  700  wherein the transferring devices  702  are movable in an orbital path  704  rather than a circular path as described in the apparatus  500  of FIGS. 10-12. The orbital path  704  of the transferring devices  702  is provided via extensible connections  706  in combination with a certain cam profile  708  of the orbital path  704 . The motors of apparatus  700  can be any suitable motor described above. FIGS. 23-25 illustrate the above embodiment including the cutting device  40  as previously shown and described above. 
     FIG. 26 illustrates another embodiment of an apparatus  750  wherein the transferring devices  752  are movable in an orbital path  754  provided by the shape of the stationary track  756  of the programmable linear motor. 
     Other alternative additional processes can include operations associated with modifying the physical dimensions, the material properties, and/or the orientation of the discrete parts in relation to the substrate to which it will be attached. Specifically, such operations can include stretching, activation, rotation and the like by any means known to those skilled in the art. For example, FIG. 27 illustrates another embodiment of the apparatus  800  of the present invention including a stretching device  802  for stretching the discrete part  804  before transferring said parts to the substrate. Further, FIG. 28 illustrates another embodiment of the apparatus  850  of the present invention including a rotating device  852  for rotating discrete parts before transferring said parts to the substrate. 
     Further, certain applications can benefit from having a flexible pitch capability. Typical examples of pitched systems include knife rolls, printing rolls, bonding rolls and the like, as well as the discrete parts transferring applications described thereinabove. The pitch of a system such as a knife roll can be typically changed by adding additional tooling on a roll (e.g., the number of knives on a roll determines the number of pitches per a revolution of a roll), however such approach is not convenient for a rapid change. Other alternatives can include varying the rotational speed of the roll, adding or subtracting spacer plates underneath the tooling to change radial distance from the axis of rotation, or operating the tooling at the appropriate cycle rate but a different surface speed from the substrate it is interacting with. The embodiments of the apparatus of the present invention described thereinabove can offer the benefit of matched speed interactions with the substrate at a desired cycle rate and without a need for physically modifying the system when changing from pitch length to pitch length, even if the pitch length varies either intentionally or unintentionally from product to product during continuous operation. 
     While particular embodiments and/or individual features of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Further, it should be apparent that all combinations of such embodiments and features are possible and can result in preferred executions of the invention. Therefore, the appended claims are intended to cover all such changes and modifications that are within the scope of this invention.